Deprecate legacy server (ruff-lsp)

[T-256]

Since native server is stable now, I think make sense to deprecate using legacy server (ruff-lsp) in VSCode extension.
Here is prototype in my branch.

[dhruvmanila]

Thanks for raising this. We did discuss this internally and the consensus is to keep it around for a little longer. I'm also going to be out on vacation soon. There was also a mention of looking into how the rls was moved to rust-analyzer (Rust language server). So, we want to explore some options but in a gist we want this to be a smooth switch for our users.