…alerts cp-7.78.0 (#30266)

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## **Description**

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Fixes release blocker regression
#30260 for release
7.78.0

## **Changelog**

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CHANGELOG entry: restores gas estimate alerts on all networks except
strictly gas-sponsored ones

## **Related issues**

Fixes: #30260

## **Manual testing steps**

Same testing intructions as for
#29835
Add non-regression for issues raised in
#30260, which may
include for example calling `pause` on [Mainnet
USDC](https://etherscan.io/token/0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48#writeProxyContract)
and checking that the "gas estimation failed" alert shows at least
somewhere (can be second alert, but it needs to exist).

## **Screenshots/Recordings**

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### **Before**

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### **After**

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- [ ] I've followed [MetaMask Contributor
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  - Ideally on a mid-range device; emulator is acceptable
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SRPs](https://consensyssoftware.atlassian.net/wiki/spaces/TL1/pages/edit-v2/401401446401?draftShareId=9d77e1e1-4bdc-4be1-9ebb-ccd916988d93)
to import wallets with many accounts and tokens
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for an example

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Changes confirmation alert gating logic for gas estimation failures
and sponsorship reserve warnings, which could alter what users see
during transaction approval on different networks. Risk is moderate
because it affects transaction UX/decisioning but does not change
signing or on-chain behavior.
> 
> **Overview**
> Restores and tightens when gas-related confirmation alerts are shown
by introducing `useIsGasSponsored`, which returns true only when
**both** the gasless transaction is supported and the current chain is
enabled via the `gasFeesSponsoredNetwork` feature flag.
> 
> `useGasEstimateFailedAlert` now suppresses the “gas estimate failed”
warning only when `useIsGasSponsored` is true (instead of suppressing
for any gasless-supported/pending checks), and
`useGasSponsorshipWarningAlert` now shows the Monad reserve-balance
blocking warning only when sponsorship is expected for the transaction.
Tests were updated and a new unit test suite was added for
`useIsGasSponsored`.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
d06ea89. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->