feat: Add region tags for Firebase AI libraries and BOM

[cartland]

Question for others: do we want to include the version numbers and other TOML configuration in the snippets? Or is this too confusing to maintain for documentation?

[snippet-bot]

Here is the summary of changes.

You are about to add 2 region tags.

• gradle/libs.versions.toml:44, tag firebase_bom_version
• gradle/libs.versions.toml:180, tag firebase_bom_libraries

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[cartland]

Changes moved to #649