[google_maps_flutter] Add Android and iOS attribution ID

[stuartmorgan-g]

Adds an attribution ID to allow association of Google Maps usage to this plugin in backend metrics. Known caveats:

• This only does Android and iOS since there's a blocker on web.
• On iOS, the necessary API was added in 9.2.0, and we still support back to 8.4.0 (for iOS 14 support), so iOS will only have attribution for apps build supporting iOS 15+ (in theory not all of those either since apps supporting iOS 15+ could have 9.0 or 9.1 in their podspec lock, but we don't expect that to be a significant number of users).

This can't be meaningfully tested because they are setters on static SDK objects that aren't inspectable. In theory we could make wrappers and then inject replacement global objects but the untestable parts of that setup would be more complex than the code in question so there's no value in doing that. Instead this will be verified on the backend. This call has no user-facing effect, so regression risk is also extremely low.

Part of flutter/flutter#168529

Pre-Review Checklist

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Footnotes

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[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

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[stuartmorgan-g]

test-exempt: can't be meaningfully tested; no client-discernable effect

[gemini-code-assist]

Code Review

This pull request adds internal usage attribution IDs for the Google Maps SDK across Android and various iOS implementations, including standard, SDK 9, and SDK 10 versions. The changes involve calling addInternalUsageAttributionId in the Android plugin and conditionally calling addInternalUsageAttributionID in the iOS plugins. Version numbers and changelogs have been updated accordingly. I have no feedback to provide.