Cleanup root build files

[daymxn]

Per b/384956859,

This migrates all of our root build files to kts. It also refactors our usages to be more inline with modern gradle practices.

Furthermore, this PR also fixes the following:

• b/384956861 -> Provide fallback for build script names

[github-actions]

📝 PRs merging into main branch

Our main branch should always be in a releasable state. If you are working on a larger change, or if you don't want this change to see the light of the day just yet, consider using a feature branch first, and only merge into the main branch when the code complete and ready to be released.

[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

[google-oss-bot]

	1 Warning
⚠️	Did you forget to add a changelog entry? (Add the 'no-changelog' label to the PR to silence this warning.)

Generated by 🚫 Danger

[github-actions]

buildSrc Test Results

37 tests   37 ✅  1m 9s ⏱️
 8 suites   0 💤
 8 files     0 ❌

Results for commit 415a0d6.

♻️ This comment has been updated with latest results.

[google-oss-bot]

Size Report ¹

Affected Products

No changes between base commit (3dd8ddf) and merge commit (15e280b).

Test Logs

• Base (3dd8ddf): https://github.com/firebase/firebase-android-sdk/actions/runs/12376946926
• Merge (15e280b): https://github.com/firebase/firebase-android-sdk/actions/runs/12400188468

1. https://storage.googleapis.com/firebase-sdk-metric-reports/RLQ9qpsNOk.html

[github-actions]

Test Results

 1 038 files  +  852   1 038 suites  +852   34m 58s ⏱️ + 29m 37s
 5 874 tests +4 640   5 852 ✅ +4 634  22 💤 + 6  0 ❌ ±0 
11 833 runs  +9 341  11 789 ✅ +9 329  44 💤 +12  0 ❌ ±0 

Results for commit 415a0d6. ± Comparison against base commit 3dd8ddf.

♻️ This comment has been updated with latest results.

[google-oss-bot]

Coverage Report ¹

Affected Products

• firebase-database

  Overall coverage changed from 50.21% (3dd8ddf) to 50.16% (15e280b) by -0.04%.

  Filename	Base (3dd8ddf)	Merge (15e280b)	Diff
  ChildChangeAccumulator.java	96.67%	83.33%	-13.33%

• firebase-firestore

  Overall coverage changed from 45.74% (3dd8ddf) to 45.73% (15e280b) by -0.01%.

  Filename	Base (3dd8ddf)	Merge (15e280b)	Diff
  DeleteMutation.java	95.24%	90.48%	-4.76%
  SetMutation.java	97.22%	94.44%	-2.78%

• firebase-installations

  Overall coverage changed from ? (3dd8ddf) to 58.17% (15e280b) by ?.

  23 individual files with coverage change

  Filename	Base (3dd8ddf)	Merge (15e280b)	Diff
  AutoValue_InstallationResponse.java	?	58.93%	?
  AutoValue_PersistedInstallationEntry.java	?	56.98%	?
  AutoValue_TokenResult.java	?	42.22%	?
  AwaitListener.java	?	0.00%	?
  Clock.java	?	0.00%	?
  CrossProcessLock.java	?	51.85%	?
  FirebaseInstallations.java	?	96.62%	?
  FirebaseInstallationServiceClient.java	?	4.80%	?
  FirebaseInstallationsException.java	?	78.57%	?
  FirebaseInstallationsRegistrar.java	?	100.00%	?
  GetAuthTokenListener.java	?	100.00%	?
  GetIdListener.java	?	70.00%	?
  IidStore.java	?	22.39%	?
  InstallationResponse.java	?	100.00%	?
  Installations.kt	?	40.00%	?
  PersistedInstallation.java	?	97.01%	?
  PersistedInstallationEntry.java	?	100.00%	?
  RandomFidGenerator.java	?	20.00%	?
  RequestLimiter.java	?	100.00%	?
  StateListener.java	?	0.00%	?
  SystemClock.java	?	100.00%	?
  TokenResult.java	?	100.00%	?
  Utils.java	?	95.00%	?

• firebase-ml-modeldownloader

  Overall coverage changed from 81.86% (3dd8ddf) to 82.11% (15e280b) by +0.25%.

  Filename	Base (3dd8ddf)	Merge (15e280b)	Diff
  FirebaseModelDownloader.java	82.21%	84.66%	+2.45%

Test Logs

• Base (3dd8ddf): https://github.com/firebase/firebase-android-sdk/actions/runs/12376946926
• Merge (15e280b): https://github.com/firebase/firebase-android-sdk/actions/runs/12400188468

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