Description

This fixes the placement of floating SnackBars to land within a safe interactive area.
SnackBarBehavior.fixed already accounts for SafeArea, and so is unaffected:

The floating behavior is not automatically wrapped in a SafeArea because its placement is dependent on other Scaffold elements, like the floating action button.

Related Issues

Fixes #64194

Tests

Floating SnackBar is placed within a SafeArea.

Checklist

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• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I signed the CLA.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I updated/added relevant documentation (doc comments with ///).
• All existing and new tests are passing.
• The analyzer (flutter analyze --flutter-repo) does not report any problems on my PR.
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Breaking Change

Did any tests fail when you ran them? Please read Handling breaking changes.

• No, no existing tests failed, so this is not a breaking change.