[tool] Support --flavor option for flutter install.

[a-wallen]

flutter install previously forced users to specify the --flavor option if flavors were configured for a flutter project, but didn't provide the option, to begin with ( see #99607 ). We could solve this by either:

1. Not throwing a tool exit when running flutter install on a project with flavors configured. Users will have to use install the application binary with the --use-application-binary flag.
2. Adding --flavor as an option - search for that flavor's binary and install it.

Fixes #99607

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

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[jmagman]

Suggest also adding flutter install --flavor and flutter install --uninstall-only --flavor to the end of https://github.com/flutter/flutter/blob/master/dev/devicelab/bin/tasks/flavors_test.dart

[jmagman]

You added Chris as me as reviewers, mark this ready for review when it's actually ready for review 🙂

[jmagman]

I didn't test this, but here's a possible way to test install in the devicelab

    await inDirectory('${flutterDirectory.path}/dev/integration_tests/flavors', () async {
      await flutter(
        'install',
        options: <String>['--flavor', 'paid'],
      );
      await flutter(
        'install',
        options: <String>['--flavor', 'paid', '--uninstall-only'],
      );
      final StringBuffer stderr = StringBuffer();
      await evalFlutter(
        'install',
        canFail: true,
        stderr: stderr,
        options: <String>['--flavor', 'bogus'],
      );

      final String stderrString = stderr.toString();
      if (!stderrString.contains('install failed, bogus flavor not found')) {
        print(stderrString);
        return TaskResult.failure('Should not succeed with bogus flavor');
      }
    });

[jmagman]

This isn't the correct error message I'm sure, you'll have to run it.

[jmagman]

This LGTM once you're done testing and the .ci.yaml bringup changes are reverted (though if you want to keep it for the Windows one, that makes sense).

[jmagman]

If the intention of this was to test in this PR, then you also need to remove presubmit: false

[christopherfujino]

Can we even run devicelab tests presubmit?

[jmagman]

We run Mac_ios hot_mode_dev_cycle_macos_target__benchmark and Linux_android hot_mode_dev_cycle_linux__benchmark so there's capacity.

But what I said doesn't make any sense, adding bringup wouldn't make it run in this PR, removing bringup would do that.

@keyonghan suggested @a-wallen do this, but I didn't see that since their conversation was resolved and hidden.

[jmagman]

LGTM

[jmagman]

This caused Windows_android flavors_test_win to start failing: #115121