dataconnect(test): Fix thread thrashing by using Dispatchers.IO in tests

[dconeybe]

This PR resolves thread thrashing and resource overhead in Firebase Data Connect unit and instrumentation tests by replacing hardcoded Dispatchers.IO with Dispatchers.Default or test-scoped StandardTestDispatcher. Additionally, it introduces cleanupsScope, a coroutine-friendly test resource cleanup utility to manage synchronous and suspending close routines safely.

Highlights

• Coroutine-Aware Cleanup Scope: Introduced cleanupsScope, a coroutine-aware utility for registering and safely executing synchronous and suspending test cleanups. It ensures proper exception propagation and suppression when block or cleanup operations fail.
• Test Dispatcher Alignment: Replaced hardcoded Dispatchers.IO and Dispatchers.Default in DataConnectGrpcRPCsUnitTest with StandardTestDispatcher bound to the test scheduler, ensuring deterministic execution and preventing thread leaks.
• Thread Thrashing Avoidance: Replaced Dispatchers.IO with Dispatchers.Default in DataConnectAuthUnitTest and TestFirebaseAppFactory to limit maximum concurrent threads, avoiding thread thrashing when spawning hundreds of background tasks.

Changelog

• Cleanups.kt
  • Added suspendingClose() to support suspending cleanup actions within a coroutine context.
  • Added CleanupsScope interface and its implementation CleanupsScopeImpl to provide a scope for registering synchronous and suspending cleanup tasks.
  • Added the cleanupsScope top-level builder to run a block of test code and guarantee execution of registered cleanups, ensuring suppressed exceptions are added to any thrown block exception.
• CleanupsUnitTest.kt
  • Added unit tests verifying cleanupsScope behavior, including return values, block exception propagation, and proper suppression of exceptions thrown during cleanup.
• DataConnectGrpcRPCsUnitTest.kt
  • Refactored tests to use the new cleanupsScope instead of manually closing resources with Cleanups().use.
  • Updated newDataConnectGrpcRPCs and cacheArb to accept a TestCoroutineScheduler and use StandardTestDispatcher for both blocking and non-blocking coroutines, making the tests more deterministic and eliminating thread-leaks.
• DataConnectAuthUnitTest.kt
  • Replaced Dispatchers.IO with Dispatchers.Default for launching concurrent background tasks to prevent thread thrashing.
  • Simplified latch execution syntax from latch.run { countDown(); await() } to latch.countDown().await().
• TestFirebaseAppFactory.kt
  • Replaced Dispatchers.IO with Dispatchers.Default for launching the delayed delete task of FirebaseApp.

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[dconeybe]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a new cleanupsScope utility in Cleanups.kt to manage resource cleanup in tests, supporting suspending cleanups and proper exception suppression. It refactors DataConnectGrpcRPCsUnitTest to use this new scope, while also migrating tests to use StandardTestDispatcher with TestCoroutineScheduler instead of hardcoded dispatchers like Dispatchers.IO or Dispatchers.Default for better test reliability. Additionally, minor dispatcher updates and code simplifications were made in TestFirebaseAppFactory and DataConnectAuthUnitTest. There are no review comments, and I have no feedback to provide.

[github-actions]

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