[google_maps_flutter] Add ground overlay support for Android and iOS

[pdenert]

Just draft PR, I'll continue to work on this, but all comments are welcome.

May fix #26479

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
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• I linked to at least one issue that this PR fixes in the description above.
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[stuartmorgan]

@pdenert Is this PR still something you are planning on completing?

[pdenert]

Yes, I'll try to back to work on this soon

[stuartmorgan]

Since this is marked as a draft and hasn't been updated in several months I'm going to close it to clean out our review queue. Please don't hesitate to submit a new PR if you decide to revisit this. Thanks!