[material_ui] Enable text_field_test

[elliette]

Port over text_field_test from flutter/flutter#184279

Work towards flutter/flutter#182636 and flutter/flutter#188395

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the AI contribution guidelines and understand my responsibilities, or I am not using AI tools.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I followed the version and CHANGELOG instructions, using semantic versioning and the repository CHANGELOG style, or I have commented below to indicate which documented exception this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

Note: The Flutter team is currently trialing the use of Gemini Code Assist for GitHub. Comments from the gemini-code-assist bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.

Footnotes

1. Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩ ↩²

[gemini-code-assist]

Code Review

This pull request removes skip annotations from bottom navigation bar and text field tests, reorganizes imports, and introduces shared test utilities including MockClipboard, FeedbackTester, and a centralized findByTooltip helper. Additionally, several text selection toolbar assertion helpers were added to the text field tests. The review feedback highlights a potential runtime type error when casting clipboard data, a potential null pointer exception in the tooltip finder, and a consistency issue where a newly added toolbar assertion helper should be made private.

[gemini-code-assist]

Code Review

This pull request re-enables the tests in text_field_test.dart by removing the @Skip annotation and resolving cross-import issues. It introduces a new MockClipboard helper class in clipboard_utils.dart and refactors text_field_test.dart to use private helper methods for toolbar assertions and wrap scroll animations in unawaited. Review feedback suggests refactoring clipboardData in MockClipboard to use Map<dynamic, dynamic>? instead of dynamic to avoid potential runtime type errors during platform channel map casting.