ruby: Support "binary" settings for Rubocop and Solargraph (#15110)

Hello, this pull request adds support for specifying and using the
"binary" settings for Rubocop and Solargraph LSPs. AFAIK, Ruby LSP does
not require the bundler context but that could be added later easily.

In Ruby world, like in Node.js world, almost all
projects rely on project specific packages (gems) and their versions.
Solargraph and Rubocop gems are usually installed as project
dependencies. Attempting to use global installation of them fail in most
cases due to incompatible or missing dependencies (gems).

To avoid that, Ruby engineers have the `bundler`
gem that provides the `exec` command. This command executes the given
command in the context of the bundle.

This pull request adds support for pulling the `binary` settings to use
them in starting both LSPs. For instance, to start the Solargraph gem in
the context of the bundler, the end user must configure the binary
settings in the folder-specific settings file like so:

```json
{
  "lsp": {
    "solargraph": {
      "binary": {
        "path": "/Users/vslobodin/Development/festivatica/bin/rubocop"
      }
    }
  }
}
```

The `path` key must be an absolute path to the `binstub` of the
`solargraph` gem. The same applies to the "rubocop" gem. Side note but
it would be awesome to use Zed specific environment variables to make
this a bit easier. For instance, we could use the `ZED_WORKTREE_ROOT`
environment variable:

```json
{
  "lsp": {
    "solargraph": {
      "binary": {
        "path": "${ZED_WORKTREE_ROOT}/bin/rubocop"
      }
    }
  }
}
```

But this is out of the scope of this pull request. The code is a bit
messy and repeatable in some places, I am happy to improve it here or
later.

References:
- https://bundler.io/v2.4/man/bundle-exec.1.html
- https://solargraph.org/guides/troubleshooting
- https://bundler.io/v2.5/man/bundle-binstubs.1.html

This pull request is based on these two pull requests:

- https://github.com/zed-industries/zed/pull/14655
- https://github.com/zed-industries/zed/issues/15001

Closes https://github.com/zed-industries/zed/issues/5109.

Release Notes:

- N/A

---------

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

docs/src/languages/ruby.md

@@ -66,6 +66,20 @@ Solargraph has formatting and diagnostics disabled by default. We can tell Zed t
 }
 ```
 
+To use Solargraph in the context of the bundle, you can use [folder-specific settings](../configuring-zed#settings-files) and specify the absolute path to the [`binstub`](https://bundler.io/v2.5/man/bundle-binstubs.1.html) of Solargraph:
+
+```json
+{
+  "lsp": {
+    "solargraph": {
+      "binary": {
+        "path": "<path_to_your_project>/bin/solargraph"
+      }
+    }
+  }
+}
+```
+
 ### Configuration
 
 Solargraph reads its configuration from a file called `.solargraph.yml` in the root of your project. For more information about this file, see the [Solargraph configuration documentation](https://solargraph.org/guides/configuration).
@@ -120,6 +134,20 @@ Rubocop has unsafe autocorrection disabled by default. We can tell Zed to enable
 }
 ```
 
+To use Rubocop in the context of the bundle, you can use [folder-specific settings](../configuring-zed#settings-files) and specify the absolute path to the [`binstub`](https://bundler.io/v2.5/man/bundle-binstubs.1.html) of Rubocop:
+
+```json
+{
+  "lsp": {
+    "rubocop": {
+      "binary": {
+        "path": "<path_to_your_project>/bin/rubocop"
+      }
+    }
+  }
+}
+```
+
 ## Using the Tailwind CSS Language Server with Ruby
 
 It's possible to use the [Tailwind CSS Language Server](https://github.com/tailwindlabs/tailwindcss-intellisense/tree/HEAD/packages/tailwindcss-language-server#readme) in Ruby and ERB files.