Migrate to composite plugin

[daymxn]

Per b/384990125,

This migrates all of our buildSrc logic into a composite plugin called plugins.

This PR makes no attempt to organize the code; that is out-of-scope for the PR.

This PR also fixes various references to buildSrc (including markdown links), to avoid any breakage.

[github-actions]

Release note changes

No release note changes were detected. If you made changes that should be
present in the next release, ensure you've added an entry in the appropriate
CHANGELOG.md file(s).

[github-actions]

Vertex AI Mock Responses Check ⚠️

A newer major version of the mock responses for Vertex AI unit tests is available. update_responses.sh should be updated to clone the latest version of the responses: v5.3

[github-actions]

plugins test results

37 tests   37 ✅  1m 18s ⏱️
 8 suites   0 💤
 8 files     0 ❌

Results for commit 1c2ecd1.

[github-actions]

Test Results

 1 038 files  + 36   1 038 suites  +36   34m 29s ⏱️ + 5m 19s
 5 874 tests +122   5 852 ✅ +123  22 💤 ±0  0 ❌  - 1 
11 833 runs  +264  11 789 ✅ +265  44 💤 ±0  0 ❌  - 1 

Results for commit 1c2ecd1. ± Comparison against base commit e3dd809.

[google-oss-bot]

Size Report ¹

Affected Products

No changes between base commit (e3dd809) and merge commit (254a2e5).

Test Logs

• Base (e3dd809): https://github.com/firebase/firebase-android-sdk/actions/runs/12402359113
• Merge (254a2e5): https://github.com/firebase/firebase-android-sdk/actions/runs/12403078448

1. https://storage.googleapis.com/firebase-sdk-metric-reports/MXDBtYyvUz.html

[google-oss-bot]

Coverage Report ¹

Affected Products

• firebase-appdistribution

  Overall coverage changed from ? (e3dd809) to 75.99% (254a2e5) by ?.

  68 individual files with coverage change

  Filename	Base (e3dd809)	Merge (254a2e5)	Diff
  AabUpdater.java	?	98.36%	?
  AabUpdater_Factory.java	?	0.00%	?
  ApkInstaller.java	?	100.00%	?
  ApkInstaller_Factory.java	?	0.00%	?
  ApkUpdater.java	?	92.63%	?
  ApkUpdater_Factory.java	?	0.00%	?
  AppDistributionReleaseImpl.java	?	100.00%	?
  AppDistributionReleaseInternal.java	?	100.00%	?
  AppDistroComponent.java	?	0.00%	?
  AppDistroComponent_MainModule_BindContentResolverFactory.java	?	0.00%	?
  AppIconSource.java	?	84.62%	?
  AppIconSource_Factory.java	?	100.00%	?
  AutoValue_AppDistributionReleaseImpl.java	?	65.45%	?
  AutoValue_AppDistributionReleaseInternal.java	?	71.58%	?
  AutoValue_ImageUtils_ImageSize.java	?	35.00%	?
  AutoValue_TesterApiDisabledErrorDetails.java	?	29.41%	?
  AutoValue_TesterApiDisabledErrorDetails_HelpLink.java	?	54.17%	?
  AutoValue_UpdateProgressImpl.java	?	65.96%	?
  DaggerAppDistroComponent.java	?	80.56%	?
  DevModeDetector.java	?	9.09%	?
  DevModeDetector_Factory.java	?	100.00%	?
  ErrorMessages.java	?	0.00%	?
  FeedbackActivity.java	?	3.39%	?
  FeedbackActivity_MembersInjector.java	?	0.00%	?
  FeedbackSender.java	?	84.48%	?
  FeedbackSender_Factory.java	?	0.00%	?
  FeedbackTrigger.java	?	61.54%	?
  FirebaseAppDistributionExceptions.java	?	80.00%	?
  FirebaseAppDistributionFileProvider.java	?	0.00%	?
  FirebaseAppDistributionImpl.java	?	89.89%	?
  FirebaseAppDistributionImpl_Factory.java	?	0.00%	?
  FirebaseAppDistributionLifecycleNotifier.java	?	91.49%	?
  FirebaseAppDistributionLifecycleNotifier_Factory.java	?	0.00%	?
  FirebaseAppDistributionNotificationsManager.java	?	88.89%	?
  FirebaseAppDistributionNotificationsManager_Factory.java	?	0.00%	?
  FirebaseAppDistributionRegistrar.java	?	95.83%	?
  FirebaseAppDistributionTesterApiClient.java	?	88.78%	?
  FirebaseAppDistributionTesterApiClient_Factory.java	?	0.00%	?
  HttpsUrlConnectionFactory.java	?	50.00%	?
  HttpsUrlConnectionFactory_Factory.java	?	100.00%	?
  ImageUtils.java	?	100.00%	?
  InstallActivity.java	?	2.67%	?
  LogWrapper.java	?	86.67%	?
  NewReleaseFetcher.java	?	86.67%	?
  NewReleaseFetcher_Factory.java	?	0.00%	?
  PackageInfoUtils.java	?	42.86%	?
  ReleaseIdentifier.java	?	91.78%	?
  ReleaseIdentifier_Factory.java	?	0.00%	?
  ReleaseUtils.java	?	83.33%	?
  ScreenshotTaker.java	?	36.17%	?
  ScreenshotTaker_Factory.java	?	0.00%	?
  SequentialReference.java	?	100.00%	?
  SignInResultActivity.java	?	0.00%	?
  SignInStorage.java	?	100.00%	?
  SignInStorage_Factory.java	?	0.00%	?
  TakeScreenshotAndStartFeedbackActivity.java	?	0.00%	?
  TakeScreenshotAndStartFeedbackActivity_MembersInjector.java	?	0.00%	?
  TaskCache.java	?	100.00%	?
  TaskCompletionSourceCache.java	?	72.41%	?
  TaskUtils.java	?	77.50%	?
  TesterApiDisabledErrorDetails.java	?	93.75%	?
  TesterApiHttpClient.java	?	90.09%	?
  TesterApiHttpClient_Factory.java	?	0.00%	?
  TesterSignInManager.java	?	95.45%	?
  TesterSignInManager_Factory.java	?	0.00%	?
  UpdateProgressImpl.java	?	100.00%	?
  UpdateTaskCache.java	?	91.30%	?
  UpdateTaskImpl.java	?	76.32%	?

• firebase-database

  Overall coverage changed from 50.22% (e3dd809) to 50.16% (254a2e5) by -0.05%.

  Filename	Base (e3dd809)	Merge (254a2e5)	Diff
  ChildChangeAccumulator.java	96.67%	83.33%	-13.33%
  DefaultPersistenceManager.java	75.73%	74.76%	-0.97%

• firebase-messaging

  Overall coverage changed from 84.04% (e3dd809) to 84.23% (254a2e5) by +0.19%.

  Filename	Base (e3dd809)	Merge (254a2e5)	Diff
  FirebaseMessaging.java	76.00%	76.80%	+0.80%
  Metadata.java	36.51%	41.27%	+4.76%

• firebase-storage

  Overall coverage changed from 83.92% (e3dd809) to 83.96% (254a2e5) by +0.04%.

  Filename	Base (e3dd809)	Merge (254a2e5)	Diff
  StreamDownloadTask.java	88.41%	88.89%	+0.48%

Test Logs

• Base (e3dd809): https://github.com/firebase/firebase-android-sdk/actions/runs/12402359113
• Merge (254a2e5): https://github.com/firebase/firebase-android-sdk/actions/runs/12403078448

1. https://storage.googleapis.com/firebase-sdk-metric-reports/dVKf9zQpr6.html