Add type hierarchy support in CodeQL

[aeisenberg]

Type hierarchies in CodeQL can be deep, especially for the core libraries. It would be very helpful for users to be able to explore the entire hierarchy in a single view.

[alexet]

There is no standard lsp support so we would have to implement it ourselves.

The closest there is to a standard is microsoft/vscode-languageserver-node#426 which is used in the java langauge server and also in theia but it was rejected without explanation by the vscode team.

[aeisenberg]

There's no standard support, and there's also no command inside of VSCode. It looks like we'd need to circumvent the LSP for this as well as create our own view for it.

[kaspersv]

Official support for type hierarchies was added in LSP v. 3.17.