Added Native Google Sign In Plugin for Android

[andygruening]

This PR includes:

• Native Google Sign-In Plugin
• Check if the .java plugin files are located inside the Project's Assets/ directory, if not, copy the files into 'Assets/Plugins/Android/
• Check if mainTemplate.gradle file exists and if it includes the required dependencies

Version Increment

Please ensure you have incremented the package version in the package.json as necessary.

• I have incremented the package.json according to semantic versioning
• No version increment is needed; the change does not impact SDK or Sample code/assets

Docs Checklist

Please ensure you have addressed documentation updates if needed as part of this PR:

• I have created a separate PR on the sequence docs repository for documentation updates: Link to docs PR
• No documentation update is needed for this change.

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