debugger beta: Fix dap_schema for DAP extensions (#31173)

We now actually call dap_schema provided by extensions instead of
defaulting to a null `serde_json::Value`. We still need to update the
Json LSP whenever a new dap is installed.

Release Notes:

- N/A

crates/extension/src/extension.rs

@@ -144,7 +144,7 @@ pub trait Extension: Send + Sync + 'static {
         worktree: Arc<dyn WorktreeDelegate>,
     ) -> Result<DebugAdapterBinary>;
 
-    async fn dap_schema(&self) -> Result<serde_json::Value>;
+    async fn get_dap_schema(&self) -> Result<serde_json::Value>;
 }
 
 pub fn parse_wasm_extension_version(