Fixes #119532

Also, adds a few features from https://www.w3.org/WAI/ARIA/apg/patterns/menubar/:

• Adds two actions to vertically-opening menu anchors (in other words, submenus that open below or above their anchor button) that allow upward and downward directional focus navigation into the menu panel (Allow MenuAnchor created menus to traverse the submenu via keyboard. #119532).
• Adds [Home] and [End] key shortcuts/actions to the menu overlay
  • [Home] moves to the first menu item
  • [End] moves to the last menu item
• Adds focus wrapping to the Submenu widget (but not the MenuAnchor widget) for non-apple platforms.
• Splits the submenu focus handling action into a submenu button action and a submenu overlay action
• Adds an overlayActions parameter to MenuAnchor to allow users to override the overlay actions.

This is a breaking change since it adds focus wrapping.

I'm open to suggestions regarding whether to add or remove more customizability to the menu shortcuts and actions. As mentioned, I'm not currently wrapping focus on the MenuAnchor but am wrapping focus on the SubmenuButton. This is because I didn't want to break existing submenus that are built atop MenuAnchor.

TODO: Migration guide.

EDIT: Waiting for #176494 to land in case animations affect focus behavior (AFAIK they should not).

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.
• I followed the breaking change policy and added Data Driven Fixes where supported.
• All existing and new tests are passing.

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