vscode: Support `TypeHierarchy` APIs

[CsCherrYY]

Feature Description:

We are working on supporting TypeHierarchy feature in vscode-java extension via LSP and there is a WIP PR here: redhat-developer/vscode-java#2376. The new version of vscode-languageclient (8.0.0+) requires API TypeHierarchyItem from vscode module, and in theia we found in https://eclipse-theia.github.io/vscode-theia-comparator/status.html, TypeHierarchyItem has not been supported yet, which causes the extension fail to activate in Theia.

Hope Theia can support the TypeHierarchy related APIs so the new implementation can work.

• TypeHierarchyItem
• TypeHierarchyProvider
• registerTypeHierarchyProvider

[vince-fugnitto]

Closed thanks to #11694.