update internal API to allow parameter label to be an offset-range of its the signature label, #56337

Introduces the concept of a re-trigger character to the signature help provider. This is a seperate set of characters that are registered with the provider. Typing a retrigger character fires a new signature help request if signature help is already showing.

#54972

debt - remove suggest adapter and use CompletionItemProvider from modes.ts. Also fixes https://github.com/Microsoft/monaco-editor/issues/985

This reverts commit 61a2faf7.

make tabCompletion be 'on' | 'off' | 'onlySnippets', only compute word end key when tab completion is enabled

* Initial work on signature help context

Fixes #54972

Adds `SignatureHelpContext`. This tells providers why signature help was requested

TODO:

- [ ] Better understand semantics of retrigger. Should `retrigger` be an flag instead of a `triggerReason`?
- [ ]  Fix skipped test
- [ ] Add more tests for trigger reasons / trigger characters

* Fix unit test

* Make sure we retrigger sig help if it is already showing

* Add test for dismiss and re-invoke

* Extract some constants

* Extract createMockEditor