Cherry-pick gradle related fixes to 6.4.x

[ippeiukai]

Platforms affected

Android

What does this PR do?

Cherry-pick gradle error fixes from master to 6.4.x:

• CB-14127: (android) Move google maven repo ahead of jcenter #450
• Always put the Google repo above jcenter #523

What testing has been done on this change?

Checklist

• Reported an issue in the JIRA database
• Commit message follows the format: "CB-3232: (android) Fix bug with resolving file paths", where CB-xxxx is the JIRA ID & "android" is the platform affected.
• Added automated test coverage as appropriate for this change.

[dpogue]

Thanks for the pull request, however the 6.4.x branch is no longer supported. I know many people are still relying on it for compatibility with some plugins, but the upcoming 7.1.2 release should allow everyone to upgrade.