[flutter_tools] Respect mustMatchAppBuild on Windows native assets

[Vonarian]

Addresses the TODO to support the mustMatchAppBuild option in the Windows native assets compiler configuration. If Visual Studio is not found and mustMatchAppBuild (throwIfNotFound) is true, throws a ToolExit. Otherwise, returns null.

This PR updates the Windows native assets compiler configuration cCompilerConfigWindows to accept a required bool throwIfNotFound parameter and respects it (resolving a pending TODO in targets.dart).

• When Visual Studio or any of its necessary tools (compiler, archiver, linker, or environment script) are missing, and throwIfNotFound is true, a ToolExit is thrown.
• Otherwise, if throwIfNotFound is false, it returns null to avoid exiting the tool in non-build scenarios.
• Unit tests have been added to verify that cCompilerConfigWindows behaves correctly in both the missing-and-required case and the missing-and-not-required case.

Fixes the pending TODO in targets.dart: // TODO(simolus3): Respect the mustMatchAppBuild option in cCompilerConfigWindows.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
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• 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.
• I followed the breaking change policy and added Data Driven Fixes where supported.
• All existing and new tests are passing.

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[gemini-code-assist]

Code Review

This pull request updates cCompilerConfigWindows to include a throwIfNotFound parameter, enabling it to throw a ToolExit when the Visual Studio toolchain is missing. The WindowsAssetTarget class was updated to pass this parameter, and unit tests were added to cover the new logic. Feedback was provided to add documentation to the updated public method to comply with the Flutter style guide.

[dcharkes]

Changes LGTM.

Kicking off CI to see if it's green.

[flutter-dashboard]

This pull request executed golden file tests, but it has not been updated in a while (20+ days). Test results from Gold expire after as many days, so this pull request will need to be updated with a fresh commit in order to get results from Gold.

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