Add label_for_symbol to extension API (#10179)

This PR adds `label_for_symbol` to the extension API.

As a motivating example, we implemented `label_for_symbol` for the
Haskell extension.

Release Notes:

- N/A

Co-authored-by: Max <max@zed.dev>

crates/extension_api/wit/since_v0.0.6/extension.wit

@@ -3,7 +3,7 @@ package zed:extension;
 world extension {
     import lsp;
 
-    use lsp.{completion};
+    use lsp.{completion, symbol};
 
     export init-extension: func();
 
@@ -117,4 +117,5 @@ world extension {
     }
 
     export labels-for-completions: func(language-server-id: string, completions: list<completion>) -> result<list<option<code-label>>, string>;
+    export labels-for-symbols: func(language-server-id: string, symbols: list<symbol>) -> result<list<option<code-label>>, string>;
 }

crates/extension_api/wit/since_v0.0.6/lsp.wit

@@ -41,4 +41,39 @@ interface lsp {
         snippet,
         other(s32),
     }
+
+    record symbol {
+        kind: symbol-kind,
+        name: string,
+    }
+
+    variant symbol-kind {
+        file,
+        module,
+        namespace,
+        %package,
+        class,
+        method,
+        property,
+        field,
+        %constructor,
+        %enum,
+        %interface,
+        function,
+        variable,
+        constant,
+        %string,
+        number,
+        boolean,
+        array,
+        object,
+        key,
+        null,
+        enum-member,
+        struct,
+        event,
+        operator,
+        type-parameter,
+        other(s32),
+    }
 }