Implement Metalava with Dackka

[daymxn]

Per b/243941807, this refactors the Dackka task to utilize Metalava generated stubs for Java sources, and use the standard sources for Kotlin.

This also adds a small extension method for Metalava, since we don't actually offer configuration of the output directory on stub generation.

[github-actions]

buildSrc Test Results

18 tests   18 ✔️  2m 12s ⏱️
  4 suites    0 💤
  4 files      0 ❌

Results for commit bed1f87.

[google-oss-bot]

Size Report ¹

Affected Products

No changes between base commit (ffd44ee) and merge commit (2aeb769).

Test Logs

• Base (ffd44ee): https://github.com/firebase/firebase-android-sdk/actions/runs/2981249718
• Merge (2aeb769): https://github.com/firebase/firebase-android-sdk/actions/runs/3003149853

Notes

• Commit (2aeb769) is created by Prow via merging PR base commit (ffd44ee) and head commit (bed1f87).

1. https://storage.googleapis.com/firebase-sdk-metric-reports/to0w0xhrHC.html

[google-oss-bot]

Coverage Report ¹

Affected Products

• firebase-database

  Overall coverage changed from 50.17% (ffd44ee) to 50.13% (2aeb769) by -0.04%.

  Filename	Base (ffd44ee)	Merge (2aeb769)	Diff
  ChildChangeAccumulator.java	96.67%	83.33%	-13.33%

• firebase-firestore

  Overall coverage changed from 44.32% (ffd44ee) to 44.42% (2aeb769) by +0.10%.

  Filename	Base (ffd44ee)	Merge (2aeb769)	Diff
  AsyncQueue.java	78.11%	78.61%	+0.50%
  Datastore.java	21.55%	23.28%	+1.72%
  FirestoreChannel.java	16.38%	18.10%	+1.72%
  FirestoreClient.java	31.25%	36.11%	+4.86%
  GrpcCallProvider.java	62.35%	69.41%	+7.06%
  IndexBackfiller.java	89.06%	93.75%	+4.69%
  LruGarbageCollector.java	90.65%	93.46%	+2.80%
  SetMutation.java	94.44%	97.22%	+2.78%
  SQLitePersistence.java	86.89%	86.34%	-0.55%

Test Logs

• Base (ffd44ee): https://github.com/firebase/firebase-android-sdk/actions/runs/2981249718
• Merge (2aeb769): https://github.com/firebase/firebase-android-sdk/actions/runs/3003149853

Notes

• Commit (2aeb769) is created by Prow via merging PR base commit (ffd44ee) and head commit (bed1f87).
• Run gradle <product>:checkCoverage to produce HTML coverage reports locally. After gradle commands finished, report files can be found under <product-build-dir>/reports/jacoco/.

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

[github-actions]

Unit Test Results

   394 files  +   343     394 suites  +343   32m 47s ⏱️ + 30m 57s
4 717 tests +3 741  4 695 ✔️ +3 719  22 💤 +22  0 ❌ ±0 
4 733 runs  +3 757  4 711 ✔️ +3 735  22 💤 +22  0 ❌ ±0 

Results for commit bed1f87. ± Comparison against base commit ffd44ee.

♻️ This comment has been updated with latest results.