test: O11Y-741 - Replace direct dispatcher usage with a provider for testing

[agrognetti]

Summary

This commit replaces direct calls to kotlinx.coroutines.Dispatchers with a DispatcherProvider abstraction. This change facilitates testing by allowing coroutine dispatchers to be overridden.

How did you test this change?

These changes are part of the test suite

Are there any deployment considerations?

No

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Note

Replace direct coroutine dispatcher usage with an injectable provider, and add test hooks and e2e rule to override dispatchers in tests.

• SDK:
  • Replace direct Dispatchers usage with DispatcherProviderHolder.current.io in InstrumentationManager, GraphQLClient, and RRwebGraphQLReplayLogExporter.
  • Add coroutines/DispatcherProvider abstraction and DispatcherProviderHolder.
• Testing:
  • Add test fixture ObservabilityDispatcherTestHooks to override SDK dispatchers.
  • Introduce TestCoroutineRule in e2e tests; update SamplingE2ETest to use @Rule and runTest.
  • Minor test cleanup in DisablingConfigOptionsE2ETest (null-check compactness).
• Build/Config:
  • Enable testFixtures in lib/build.gradle.kts; add testFixturesImplementation for coroutines-test.
  • In e2e app, depend on testFixtures(project(":observability-android")).
  • Set android.experimental.enableTestFixturesKotlinSupport=true in gradle.properties.

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