CI: add Android JVM unit test execution to PR workflow

Problem

The PR CI workflow (.github/workflows/build-pr.yml → .github/workflows/eslint.yml) runs yarn lint and yarn test --runInBand (Jest), then chains the Android/iOS build workflows.

It does not execute Android JVM unit tests (./gradlew :app:testDebugUnitTest). The build-android workflow runs assembleRelease, which catches compile errors but doesn't execute the test sources under android/app/src/test/.

This means tests like MediaCallsAnswerRequestTest.kt (added in https://github.com/RocketChat/Rocket.Chat.ReactNative/pull/7245), DDPClientTest.kt, MediaCallsRegistryTest.kt, etc. only run when a developer remembers to invoke them locally.

Suggested fix

Add a ./gradlew :app:testDebugUnitTest step to the PR workflow — either:

1. As a new step in eslint.yml after the Jest run, or
2. As a separate android-unit-tests.yml workflow gated on pull_request.

Option 2 keeps the JS+TS lint/test job lean and lets Android JVM tests run in parallel.

Why now

The release-readiness queue added several Android JVM test classes (#7245 has 276 lines of MockWebServer coverage). Without CI execution, regressions in the timeout / dedupe / dispatch logic land silently. Filing as a follow-up so the test suite gets actual gating value.

Start by reading .github/workflows/build-pr.yml and .github/workflows/eslint.yml to trace the existing PR checks and Android workflow chaining. Add execution of ./gradlew :app:testDebugUnitTest in the selected PR workflow arrangement, then verify that the Android JVM tests run and that a failing test causes the workflow to fail.