extension: Add capabilities for the process API (#26224)

This PR adds support for capabilities for the extension process API.

In order to use the process API, an extension must declare which
commands it wants to use, with arguments:

```toml
[[capabilities]]
kind = "process:exec"
command = "echo"
args = ["hello!"]
```

A `*` can be used to denote a single wildcard in the argument list:

```toml
[[capabilities]]
kind = "process:exec"
command = "echo"
args = ["*"]
```

And `**` can be used to denote a wildcard for the remaining arguments:

```toml
[[capabilities]]
kind = "process:exec"
command = "ls"
args = ["-a", "**"]
```

Release Notes:

- N/A

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

extensions/test-extension/extension.toml

@@ -13,3 +13,8 @@ language = "Gleam"
 [grammars.gleam]
 repository = "https://github.com/gleam-lang/tree-sitter-gleam"
 commit = "8432ffe32ccd360534837256747beb5b1c82fca1"
+
+[[capabilities]]
+kind = "process:exec"
+command = "echo"
+args = ["hello!"]

extensions/test-extension/src/test_extension.rs

@@ -1,6 +1,7 @@
 use std::fs;
 use zed::lsp::CompletionKind;
 use zed::{CodeLabel, CodeLabelSpan, LanguageServerId};
+use zed_extension_api::process::Command;
 use zed_extension_api::{self as zed, Result};
 
 struct TestExtension {
@@ -13,6 +14,10 @@ impl TestExtension {
         language_server_id: &LanguageServerId,
         _worktree: &zed::Worktree,
     ) -> Result<String> {
+        let echo_output = Command::new("echo").arg("hello!").output()?;
+
+        println!("{}", String::from_utf8_lossy(&echo_output.stdout));
+
         if let Some(path) = &self.cached_binary_path {
             if fs::metadata(path).map_or(false, |stat| stat.is_file()) {
                 return Ok(path.clone());