[google_sign_in] Implement hosted domain on Android

[stuartmorgan-g]

Adds support for hosted domain filtering on Android. This was wired up for authorize (which would apply when calling authorize without a user set), but not for authenticate, because the first draft of Android support only used the one-tap flow, which doesn't have domain filter support, and I forgot to add it when I added the button flow.

Because one-tap doesn't support the filtering feature, this adjusts the way the attemptLightweightAuthentication is handled when a filter is set. Instead of following the usual guidance to call it first with filterToAuthorized and autoSelectEnabled (for returning sign-in), then again without (for one-tap UI), it will only do the first call, which means it will allow returning sign-ins, but not show a general one-tap selection UI that could allow seleting an account that doesn't meet the filter requirement. (In theory, there are cases where this would be wrong if someone changed their filtering dynamically from run to run, but I can't imagine why that would be done, and in that case there's nothing that can be done with the current SDK support anyway, so if someone really wants to do that they need to just not call attemptLightweightAuthentication.)

Also updates to the latest version of Pigeon since I was regenerating the Pigeon files already.

Fixes flutter/flutter#174200

Pre-Review Checklist

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[gemini-code-assist]

Code Review

This pull request successfully implements hostedDomain filtering on Android for Google Sign-In. The changes are well-implemented across the native and Dart layers, including necessary updates to the Pigeon communication files. The logic correctly handles the limitations of the one-tap sign-in flow, which doesn't support domain filtering. New tests have been added to cover the new functionality. The only issue I've found is a minor formatting problem in the CHANGELOG.md file.