Add supported commands in server capabilities (#11850)

## Summary

This PR updates the server capabilities to include the commands that
Ruff supports. This is similar to how there's a list of possible code
actions supported by the server.

I noticed this when I was trying to find whether Helix supported
workspace commands or not based on Jane's comment
(https://github.com/astral-sh/ruff/pull/11831#discussion_r1634984921)
and I found the `:lsp-workspace-command` in the editor but it didn't
show up anything in the picker.

So, I looked at the implementation in Helix
(9c479e6d2d/helix-term/src/commands/typed.rs (L1372-L1384))
which made me realize that Ruff doesn't provide this in its
capabilities. Currently, this does require `ruff` to be first in the
list of language servers in the user config but that should be resolved
by https://github.com/helix-editor/helix/pull/10176. So, the following
config should work:

```toml
[[language]]
name = "python"
# Ruff should come first until https://github.com/helix-editor/helix/pull/10176 is released
language-servers = ["ruff", "pyright"]
```

## Test Plan

1. Neovim's server capabilities output should include the supported
commands:

```
  executeCommandProvider = {                                                                                                                          
    commands = { "ruff.applyFormat", "ruff.applyAutofix", "ruff.applyOrganizeImports", "ruff.printDebugInformation" },                                
    workDoneProgress = false                                                                                                                          
  },
```

2. Helix should now display the commands to pick from when
`:lsp-workspace-command` is invoked:

<img width="832" alt="Screenshot 2024-06-13 at 08 47 14"
src="09048ecd-c974-4e09-ab56-9482ff3d780b">

crates/ruff_server/src/server.rs

@@ -1,6 +1,7 @@
 //! Scheduling, I/O, and API endpoints.
 
 use std::num::NonZeroUsize;
+use std::str::FromStr;
 
 use lsp_server as lsp;
 use lsp_types as types;
@@ -276,6 +277,14 @@ impl Server {
                     },
                 },
             )),
+            execute_command_provider: Some(types::ExecuteCommandOptions {
+                commands: SupportedCommand::all()
+                    .map(|command| command.identifier().to_string())
+                    .to_vec(),
+                work_done_progress_options: WorkDoneProgressOptions {
+                    work_done_progress: Some(false),
+                },
+            }),
             hover_provider: Some(types::HoverProviderCapability::Simple(true)),
             notebook_document_sync: Some(types::OneOf::Left(NotebookDocumentSyncOptions {
                 save: Some(false),
@@ -354,3 +363,56 @@ impl SupportedCodeAction {
         .into_iter()
     }
 }
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub(crate) enum SupportedCommand {
+    Debug,
+    Format,
+    FixAll,
+    OrganizeImports,
+}
+
+impl SupportedCommand {
+    const fn label(self) -> &'static str {
+        match self {
+            Self::FixAll => "Fix all auto-fixable problems",
+            Self::Format => "Format document",
+            Self::OrganizeImports => "Format imports",
+            Self::Debug => "Print debug information",
+        }
+    }
+
+    /// Returns the identifier of the command.
+    const fn identifier(self) -> &'static str {
+        match self {
+            SupportedCommand::Format => "ruff.applyFormat",
+            SupportedCommand::FixAll => "ruff.applyAutofix",
+            SupportedCommand::OrganizeImports => "ruff.applyOrganizeImports",
+            SupportedCommand::Debug => "ruff.printDebugInformation",
+        }
+    }
+
+    /// Returns all the commands that the server currently supports.
+    const fn all() -> [SupportedCommand; 4] {
+        [
+            SupportedCommand::Format,
+            SupportedCommand::FixAll,
+            SupportedCommand::OrganizeImports,
+            SupportedCommand::Debug,
+        ]
+    }
+}
+
+impl FromStr for SupportedCommand {
+    type Err = anyhow::Error;
+
+    fn from_str(name: &str) -> anyhow::Result<Self, Self::Err> {
+        Ok(match name {
+            "ruff.applyAutofix" => Self::FixAll,
+            "ruff.applyFormat" => Self::Format,
+            "ruff.applyOrganizeImports" => Self::OrganizeImports,
+            "ruff.printDebugInformation" => Self::Debug,
+            _ => return Err(anyhow::anyhow!("Invalid command `{name}`")),
+        })
+    }
+}