peek type hierarchy

[Eskibear]

Part of #15533 This PR adds UI for "Peek Type Hierarchy".

CSS file and common data structures (e.g. State, LayoutInfo) are copied from call hierarchy implementation. It would be better to extract them to a proper place.

[Eskibear]

I tested it with a mock extension, with type hierarchy provider implemented for plaintext files. Each word represents a type, inheriting all types from previous line.

peek-type-h.mp4

[jrieken]

Thanks. This looks good despite being mostly identical to the call hierarchy peek. I will proceed with merging so that we have this in the product and then I will spend some cycles to reduce the duplication.

[Eskibear]

Thank you. I was just trying to get it working, and it definitely requires you vscode expert to refine the code.

And one thing to mention, I assigned the same alt-shift-h keybinding with call-h that I'm not sure about potential conflicts.

[jrieken]

I assigned the same alt-shift-h keybinding with call-h that I'm not sure about potential conflicts.

Yeah, that I removed for now. We can try to find a better one but most are in use unfortunately.