vscode: add support for inlay hints

[vince-fugnitto]

What it does

Closes: #10978.

The pull-request adds support for inlay hints in the editor:

How to test

In order to verify inlay hints, I build a newer version of the typescript builtins (v1.65.0) which included the feature.

1. checkout the branch, and build the changes
2. remove the plugins folder, and instead add the following extensions (typescript-builtins-1.65.0.zip)
3. start the application using theia itself as a workspace
4. ensure that the following preferences are turned on:

   "editor.inlayHints.enabled": "on"
   "typescript.inlayHints.enumMemberValues.enabled": true,
   "typescript.inlayHints.functionLikeReturnTypes.enabled": true,
   "typescript.inlayHints.parameterNames.enabled": "all",
   "typescript.inlayHints.parameterTypes.enabled": true,
   "typescript.inlayHints.propertyDeclarationTypes.enabled": true,
   "typescript.inlayHints.variableTypes.enabled": true,

5. ensure that the workspace is using at least typescript@4.4.0 as a version which includes support for inlay hints
6. open a typescript file and confirm that inlay hints are in fact present

Additional Information

• CQ

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

Signed-off-by: vince-fugnitto vincent.fugnitto@ericsson.com

[msujew]

Well done, that looks really good :)

I can confirm that the feature works as expected and provides support for the full inlay hints API (see below)

• Inlay hints are provided by extensions as expected and work just like in vscode
• They can be disabled using the preference. All entries of the preference work as indicated

I have a few minor improvements to the code, but I'll approve this already 👍

[vince-fugnitto]

@msujew thank you for the detailed review, I updated the code with your suggestions.

[JonasHelming]

@vince-fugnitto CQ is approved, I guess we can merge this?