Implement type hierarchy

In LSP 3.17.0, [type hierarchy requests](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_prepareTypeHierarchy) (textDocument/typeHierarchy) was introduced. Can be super useful when you have more than one super type, or subtype, and want to see how everything fit together. Sometimes we have complex inheritance structures, especially when using Java code...

Might look into this myself if I find the time, but making an issue so we don't forget about it.

Start with the linked LSP 3.17.0 textDocument/prepareTypeHierarchy specification to understand the required type-hierarchy requests. No repository files, tests, or entry points are named; done means supporting type hierarchy requests for navigating supertypes and subtypes, with appropriate coverage added.

Written by the indexing model from the issue text.