Add aria menu roles to menu-related widgets (#164741)
Related to https://github.com/flutter/flutter/issues/157177
This PR is to add the following changes:
* Implement `SemanticsRole.menu`, `SemanticsRole.menuItem`,
`SemanticsRole.menuBar`, `SemanticsRole.menuItemCheckbox`, and
`SemanticsRole.menuItemRadio`.
* Add `SemanticsRole.menu` role in ~`MenuAnchor`~, `DropdownButton`, and
`PopupMenuButton`
~* Add `SemanticsRole.menuBar` role to `MenuBar`~
* Add `SemanticsRole.menuItem` to ~`MenuItemButton`~, `DropdownMenuItem`
and `PopupMenuItem`
~* Add `SemanticsRole.menuItemCheckbox` to `CheckboxMenuButton`~
~* Add `SemanticsRole.menuItemRadio` to `RadioMenuButton`~
## Pre-launch Checklist
- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [ ] I listed at least one issue that this PR fixes in the description
above.
- [x] 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].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [ ] All existing and new tests are passing.
If you need help, consider asking for advice on the #hackers-new channel
on [Discord].
<!-- Links -->
[Contributor Guide]:
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[Tree Hygiene]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md
[test-exempt]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes
[Discord]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md
[Data Driven Fixes]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md
32b34ff99e