Distribute FTL tests amongst different device models

[jonsimantov]

Description

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

Distributing the load will help prevent issues with a single FTL device type from bottlenecking the tests.

Depends on FirebaseExtended/github-actions#7 being merged and a new release of the firebase-test-lab action created.

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Testing

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

Running expanded tests on this PR.

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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.

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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 FAILED

Requested by @jonsimantov on commit b50057e
Last updated: Thu Oct 12 15:09 PDT 2023
View integration test log & download artifacts

Failures	Configs
missing_log	[TEST] [ERROR] [Android] [All 3 os] [1/2 android_device: android_target]
gma	[TEST] [FAILURE] [iOS] [macos] [1/2 ios_device: ios_target] (1 failed tests)   FirebaseGmaUmpTest.TestUmpMethodsReturnOperationInProgress
storage	[TEST] [FLAKINESS] [iOS] [macos] [1/2 ios_device: ios_target] (1 failed tests)   FirebaseStorageTest.TestWriteAndReadFileWithCustomMetadata

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

[sunmou99]

LGTM