Update Android SDK versions for I/O release.

[jonsimantov]

Description

Provide details of the change, and generalize the change in the PR title above.

Changes in this update:

• Raise minSdkVersion to 21
• Raise targetSdkVersion to 34
• Raise compileSdkVersion to 34
• Add android:exported="true" to AndroidManifest.xml files

---

Testing

Describe how you've tested these changes. Link any manually triggered Integration tests or CPP binary SDK Packaging Github Action workflows, if applicable.

Testing via integration tests in this PR.

---

Type of Change

Place an x the applicable box:

• Bug fix. Add the issue # below if applicable.
• New feature. A non-breaking change which adds functionality.
• Other, such as a build process or documentation change.

---

Notes

• Bug fixes and feature changes require an update to the Release Notes section of release_build_files/readme.md.
• Read the contribution guidelines CONTRIBUTING.md.
• Changes to the public API require an internal API review. If you'd like to help us make Firebase APIs better, please propose your change in a feature request so that we can discuss it together.

[github-actions]

Integration test with FLAKINESS (succeeded after retry)

Requested by @jonsimantov on commit de498a6
Last updated: Wed May 1 13:56 PDT 2024
View integration test log & download artifacts

Failures	Configs
app_check	[TEST] [FLAKINESS] [Android] [1/3 os: ubuntu] [1/2 android_device: android_target] (1 failed tests)   CRASH/TIMEOUT [TEST] [FLAKINESS] [Android] [1/3 os: windows] [1/2 android_device: emulator_ftl_target] (3 failed tests)   FirebaseAppCheckTest.TestAddTokenChangedListener   FirebaseAppCheckTest.TestGetTokenForcingRefresh   FirebaseAppCheckTest.TestGetTokenLastResult
remote_config	[TEST] [FLAKINESS] [Android] [1/3 os: ubuntu] [1/2 android_device: android_target] (1 failed tests)   FirebaseRemoteConfigTest.TestFetchSecondsParameter

Add flaky tests to go/fpl-cpp-flake-tracker