Previously, `decodeVerifiedReward` silently returned `.noReward` for any
of: missing reward key, null reward, or non-object reward value (e.g. a
string/number/array). The first two are expected; the last indicates a
backend mismatch and should be surfaced.

Now distinguish:
- absent or null reward → `.noReward` (silent, expected)
- present but not a JSON object → `.unsupportedReward` + `Logger.warn`

This matches the existing convention in this file of logging warnings
when decoding unrecognized/malformed values into fallback cases.

Align reward payload modeling with backend semantics by decoding `amount` as Int and updating tests to reject fractional values as malformed rewards.

…apter

First step in regrouping the AdMob adapter under a single namespace.

Internal-only refactor — no public API changes:
* New `Tracking` umbrella enum (caseless) holds `Adapter`, `Tracker`,
  `PurchasesTracker`.
* `RCAdMob` class → `Tracking.Adapter`; its file is split into
  `Tracking/{Tracking,Adapter,Tracker,PurchasesTracker}.swift`.
* `AdTracking` protocol → `Tracking.Tracker`.
* `PurchasesAdTracker` → `Tracking.PurchasesTracker`.
* `rcAdMob:` parameter / `rcAdMob` property → `adapter:` / `adapter`
  across the four delegate wrappers, the GMA `loadAndTrack` extensions,
  and tests.

The four `RCAdMob*` delegate wrapper class names, `RCFullScreenAdTracking`,
and the `Tracking/` file moves of the wrappers themselves are deferred to
commit 2 for a smaller diff per step.

Move every adapter file into the Tracking/ subfolder and drop the RC*/
RCAdMob* prefixes by nesting the types inside the Tracking namespace.

File moves (git mv preserves history):
- RCAdMobBannerViewDelegate.swift          -> Tracking/BannerViewDelegate.swift
- RCAdMobFullScreenContentDelegate.swift   -> Tracking/FullScreenContentDelegate.swift
- RCAdMobNativeAdDelegate.swift            -> Tracking/NativeAdDelegate.swift
- RCAdMobNativeAdLoader.swift              -> Tracking/AdLoader+Tracking.swift
- BannerView+RCAdMob.swift                 -> Tracking/BannerView+Tracking.swift
- FullScreenAd+RCAdMob.swift               -> Tracking/FullScreenAd+Tracking.swift
- FullScreenAd+RCAdMob+Completion.swift    -> Tracking/FullScreenAd+Tracking+Completion.swift

Type renames (all internal):
- RCAdMobBannerViewDelegate         -> Tracking.BannerViewDelegate
- RCAdMobFullScreenContentDelegate  -> Tracking.FullScreenContentDelegate
- RCAdMobNativeAdDelegate           -> Tracking.NativeAdDelegate
- RCNativeAdLoaderDelegateProxy     -> Tracking.NativeAdLoaderDelegateProxy
  (kept "Proxy" suffix to avoid clashing with GoogleMobileAds.NativeAdLoaderDelegate)
- RCFullScreenAdTracking (protocol) -> Tracking.FullScreenAd
- FullScreenLoadContext (struct)    -> Tracking.FullScreenLoadContext
- rcSetTrackingFullScreenContentDelegate (helper on the protocol)
                                    -> setTrackingDelegate on Tracking.FullScreenAd
- private file-scoped key enums lose RC prefix
  (RCBannerAssociatedKeys -> BannerAssociatedKeys,
   RCNativeAdLoaderAssociatedKeys -> NativeAdLoaderAssociatedKeys)

Public API surface is unchanged: setTrackingFullScreenContentDelegate(_:),
loadAndTrack(...), and present(from:placement:...) keep their signatures and
behavior; only the internal helpers they forward to were renamed.

Test files still use their RCAdMob* filenames (deferred to commit 6); only
the type references inside them were updated.

Verified: swift build, xcodebuild test on iOS Simulator (87 tests passing),
swiftlint clean.

Move the Obj-C associated-object retention logic for the full-screen
content tracking delegate out of Tracking.Adapter into a dedicated
Tracking.FullScreenDelegateStore type that owns the associated-object key
and exposes retain/retrieve operations.

Tracking.Adapter holds an instance and exposes it directly so callers
reach for adapter.fullScreenDelegateStore.{retain,retrieve}(...) instead
of the previous retainFullScreenDelegate / retrieveFullScreenDelegate
facades on Adapter.

Behavior is identical (still uses OBJC_ASSOCIATION_RETAIN_NONATOMIC).
Public API unchanged. Verified with iOS Simulator test run (87/87 passing).

Move the Obj-C associated-object retention logic for the native ad
tracking delegate out of Tracking.Adapter into a dedicated
Tracking.NativeDelegateStore type that owns the associated-object key
and exposes the retain operation.

Tracking.Adapter holds an instance and exposes it directly so callers
reach for adapter.nativeDelegateStore.retain(...) instead of the previous
retainNativeDelegate facade on Adapter.

Behavior is identical (still uses OBJC_ASSOCIATION_RETAIN_NONATOMIC).
Public API unchanged. Verified with iOS Simulator test run (87/87 passing).

Move the Obj-C associated-object retention logic for the native
ad-loader delegate proxy out of GoogleMobileAds.AdLoader.loadAndTrack
into a dedicated Tracking.NativeAdLoaderProxyStore type that owns the
associated-object key and exposes the retain operation.

Tracking.Adapter holds an instance and exposes it directly, so the
AdLoader extension reaches for adapter.nativeAdLoaderProxyStore.retain(...)
instead of using a private file-scoped associated-object key with
objc_setAssociatedObject inline.

Behavior is identical (still uses OBJC_ASSOCIATION_RETAIN_NONATOMIC).
Public API unchanged. Verified with iOS Simulator test run (87/87 passing).

This completes the symmetry across the three delegate stores
(FullScreenDelegateStore, NativeDelegateStore, NativeAdLoaderProxyStore),
each owning a single associated-object key and a single responsibility.

Drop the RCAdMob* prefix from all adapter test files and class names so
the test suite matches the namespacing used by the production sources
(Tracking.* in Sources/RevenueCatAdMob/Tracking/).

File and class renames:
- RCAdMobTestCase.swift                       -> AdapterTestCase.swift
  (typealias RCAdMobTestCase -> AdapterTestCase)
- RCAdMobAPISurfaceTests.swift                -> APISurfaceTests.swift
- RCAdMobBannerDelegateForwardingTests.swift  -> BannerDelegateForwardingTests.swift
- RCAdMobBannerPaidHandlerBehaviorTests.swift -> BannerPaidHandlerBehaviorTests.swift
- RCAdMobBannerWrapperBehaviorTests.swift     -> BannerWrapperBehaviorTests.swift
- RCAdMobDelegateContractTests.swift          -> DelegateContractTests.swift
- RCAdMobFullScreenDelegateForwardingTests.swift
                                              -> FullScreenDelegateForwardingTests.swift
- RCAdMobNativeAdLoaderProxyBehaviorTests.swift
                                              -> NativeAdLoaderProxyBehaviorTests.swift
- RCAdMobNativeDelegateForwardingTests.swift  -> NativeDelegateForwardingTests.swift
- RCAdMobPrecisionMappingTests.swift          -> PrecisionMappingTests.swift
- RCAdMobRevenueConversionTests.swift         -> RevenueConversionTests.swift
- RCAdMobTrackingTests.swift                  -> AdapterTrackingTests.swift
  (also renames the secondary RCAdMobDelegateTrackingTests class within
   the file to AdapterDelegateTrackingTests)

Split RCAdMobDelegateRetentionTests.swift into per-store test files,
mirroring the store extractions:
- FullScreenDelegateStoreTests.swift — exercises Tracking.Adapter
  .fullScreenDelegateStore.retain(_:for:)
- NativeDelegateStoreTests.swift     — exercises Tracking.Adapter
  .nativeDelegateStore.retain(_:for:)

No production code changes. Verified with iOS Simulator test run
(87/87 passing).