ruby: Add ruby-lsp as an experimental language server (#11768)

Adds [ruby-lsp](https://shopify.github.io/ruby-lsp/) as an alternative
LS for Ruby language.
While support for fully functional `ruby-lsp` is limited due to some
limitations (see https://github.com/zed-industries/zed/pull/8613) I
think it's OK to add it but disable by default. Thanks!

Resolves #4834.

Release Notes:

- N/A

### Some screenshots

Completion support
![CleanShot 2024-05-13 at 22 58
23@2x](https://github.com/zed-industries/zed/assets/1894248/d5047baa-c58f-465d-ae31-a7045aa56adf)

Symbol search
![CleanShot 2024-05-13 at 23 03
59@2x](https://github.com/zed-industries/zed/assets/1894248/0cb6320a-b000-4a0c-85eb-f8d1a8f6936e)

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Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>