Extract Ruby extension (#11360)

This PR extracts Ruby and ERB support into an extension and removes the
built-in Ruby and Ruby support from Zed.

As part of this, the new extension is prepared for adding support for
the `Ruby LSP` which has some blockers. See
https://github.com/zed-industries/zed/pull/8613 I was thinking of adding
an initial support for Ruby LSP but I think it would be better to start
with extracting the Ruby extension for now.

The implementation, as the 1st step, matches the bundled version but
with 3 differences:

1. Added signature output to the completion popup. See my comment below.
![CleanShot 2024-05-04 at 09 17
37@2x](https://github.com/zed-industries/zed/assets/1894248/486b7a48-ea0c-44ce-b0c9-9f8f5d3ad42d)

3. Use the shell environment for starting the `solargraph` executable.
See my comment below.
4. Bumped the tree sitter version for Ruby to the latest available
version.

Additionally, I plan to tweak this extension a bit in the future but I
think we should do this bit by bit. Thanks!

Release Notes:

- Removed built-in support for Ruby, in favor of making it available as
an extension.

---------

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

Cargo.lock

@@ -5720,7 +5720,6 @@ dependencies = [
  "tree-sitter-proto",
  "tree-sitter-python",
  "tree-sitter-regex",
- "tree-sitter-ruby",
  "tree-sitter-rust",
  "tree-sitter-typescript",
  "tree-sitter-yaml",
@@ -13114,6 +13113,13 @@ dependencies = [
  "zed_extension_api 0.0.4",
 ]
 
+[[package]]
+name = "zed_ruby"
+version = "0.0.1"
+dependencies = [
+ "zed_extension_api 0.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "zed_svelte"
 version = "0.0.1"