Performance benchmark

[bentsherman]

We should have a benchmark that simulates typical language server operations (e.g. open a workspace, open some files, edit, rename, navigate, etc). It will serve as an integration test, a performance health check, and as a way to evaluate potential performance optimizations.

See also:

• Deno LS blog post: https://deno.com/blog/optimizing-our-lsp
  • benchmark: https://github.com/denoland/deno/blob/03a76f33ad0808c659116721a757958ad054dd25/cli/bench/lsp.rs#L77-L141
  • flamegraphs to identify performance bottlenecks
• rust-analyzer syntax: https://github.com/rust-lang/rust-analyzer/blob/master/docs/dev/syntax.md
  • alternate syntax representations could reduce memory usage, but need to test
• https://code.visualstudio.com/api/language-extensions/language-server-extension-guide#testing-the-language-server