Wait to signal to the extHostTerminalService that the terminal is opened until the terminal has a name. (#58983)

Also added a change listener for title. Fixes #53057

* 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

- Send exthost logs location from renderer
- IExtensionService: Expose an API to get exthost logs location

This reverts commit 1f7ce421.

This reverts commit 95c0e072.

Fixes #56217