Consider switching from tower_lsp to something else

[ratmice]

While tower_lsp has been great, because of the lifetime bounds on the traits we end up spinning up threads for the parsers and communicating between the lsp thread and the parse threads via channels, because the parsers cannot be held across await points, and there isn't a means to instantiate the server in a local set afaict.

This use of multiple threads then has an impact on porting to wasm and also means we're split between async and sync parts of the codebase. So it would probably be worthwhile to cut our losses and migrate to the lsp-server crate or something else.