…ct. (#2062)

Flutter is migrating from CocoaPods to Swift Package Manager to manage native dependencies on iOS and macOS. We'd like to answer the following questions:

1. Does the Swift Package Manager feature increase error rates?
2. Can we remove CocoaPods support from Flutter's tooling?
3. Can we tell plugin authors that they can remove CocoaPods integration from their plugins? 

This adds a telemetry event that Flutter will send when it injects plugins into an iOS or macOS project. This will happen whenever a user does commands like `flutter build ios`, `flutter build macos`, and more.

Part of flutter/flutter#147602

Flutter PR: flutter/flutter#166773

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…ter/flutter#166773)

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Flutter is migrating from CocoaPods to Swift Package Manager to manage
native dependencies on iOS and macOS. We'd like to answer the following
questions:

1. Can we remove CocoaPods support from Flutter's tooling?
2. Can we tell plugin authors that they can remove CocoaPods integration
from their plugins?

This makes the Flutter tool send an event when it injects plugins into
an iOS or macOS project. This will happen whenever a user does commands
like `flutter build ios`, `flutter build macos`, and more.

Part of flutter#147602

Depends on: dart-lang/tools#2062

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview
[Tree Hygiene]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md
[test-exempt]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes
[Discord]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md
[Data Driven Fixes]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

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