Make accessibility help generic

[Tyriar]

Currently we have a few different accessibility help dialogs that appear, for example:

Editor:

Terminal:

Chat view:

They each work similar but have different implementations and different commands (they probably share some code, I'm not sure).

My proposal is to have a single command "Show Accessibility Help" bound to alt+f1 across the whole workbench, components can register their own custom text which ends up showing in a centered monaco editor. From there we can trap the focus on the editor and escape or clicking out of the dialog would hide it and return focus to the previous activeElement.

The presentation of it could look similar to the editor dialog but have a monaco editor inside instead. It could also have a 50% black background to give a strong indication that you can click here to get out. The actual visual presentation isn't too important but with a single implementation we can make it look good just one time.

This would lead to a consistent experience across all components that use it, shared implementation, a single lazy loaded monaco editor that's only constructed when needed and it wouldn't lead to potential issues such as getting the content and the help message mixed up when it's currently sharing an editor.

cc @jooyoungseo

[meganrogge]

Will address #184176

[Tyriar]

@meganrogge should this be reopened to track all the follow ups in #184435?

[meganrogge]

Remaining help menu adoption:

• notebook Add notebook accessibility help menu #184176
• editor make accessibility help menu more accessible #179689
• diff editor - after that refactor has happened add accessible help menu for diff editor #185028
• merge editor - after bug fixes merge editor accessible help menu #185029

To do later:

• adopt in hovers Use AccessibleView for hovers #184620
• chat responses https://github.com/microsoft/vscode-copilot/issues/284
• notebook output cells Accessibility feature in output cell of notebook with VsCode #183208
• improve inline chat menu https://github.com/microsoft/vscode-copilot/issues/313
• add a way to view next/previous content in AccessibleView #184612
• Consider using AccessibleView as the basis of TerminalAccessibleBuffer #184622
• add border around accessible view #184618
• Provide way for users to disable accessibility.verbosity setting from within help menu #185127

[meganrogge]

All issues addressed besides the ones that will be handled by @amunger and @hediet