collab: Add the ability to filter extensions by what they provide (#24315)

This PR adds the ability to filter extension results from the extension
API by the features that they provide.

For instance, to filter down just to extensions that provide icon
themes:

```
https://api.zed.dev/extensions?provides=icon-themes
```

Release Notes:

- N/A

crates/rpc/src/extension.rs

@@ -1,8 +1,9 @@
 use std::collections::BTreeSet;
+use std::sync::Arc;
 
 use chrono::{DateTime, Utc};
 use serde::{Deserialize, Serialize};
-use std::sync::Arc;
+use strum::EnumString;
 
 #[derive(Clone, Serialize, Deserialize, Debug, PartialEq)]
 pub struct ExtensionApiManifest {
@@ -17,8 +18,11 @@ pub struct ExtensionApiManifest {
     pub provides: BTreeSet<ExtensionProvides>,
 }
 
-#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy, Serialize, Deserialize)]
+#[derive(
+    Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy, Serialize, Deserialize, EnumString,
+)]
 #[serde(rename_all = "kebab-case")]
+#[strum(serialize_all = "kebab-case")]
 pub enum ExtensionProvides {
     Themes,
     IconThemes,