Add opentelemetry support

It would be nice to (optionally?) build `lsp` with opentelemetry support. Probably using `hs-opentelemetry-api` as that's the new and actively developed one?

At least I think it would be helpful to trace every handler, and add the request and response data as attributes.

The issue names no files, tests, or entry points. First map how lsp is built and where request handlers are defined, then determine how optional hs-opentelemetry-api support would be integrated; done should include an optional build and tracing for every handler with request and response data as attributes.

Written by the indexing model from the issue text.