Support inlay hint parts

[mjbvz]

From microsoft/vscode#129528

Search terms

• inlay hint
• Symbol

Feature request

VS Code's inlay hints now support parts:

https://github.com/microsoft/vscode/blob/1a500916671d65ee24484c3fca41a9cd243dd54f/src/vscode-dts/vscode.d.ts#L4848

This allows users to interact with individual works within the inlay hint. For JS/TS, we should use this for type inlay hints to allow the user to click into specific types

For example, if the inlay hint is : a | b, there would be four parts:

1. :
2. a — And clicking on it should go to the symbol a
3. |
4. b — And clicking on it should go to the symbol b

These parts can be resolved lazily too if computing them in the original request is too expensive

[mjbvz]

Actually this is already tracked by #47693