extension: Add support for additional_workspace_configuration and additional_initialization_options (#27407)

Closes #22410

With this PR extensions can provide additional workspace configuration
for other LSP Adapters. This allows extensions like Astro, Svelte, Vue,
etc to provide plugins for vtsls typescript server, fixing issues like:
https://github.com/zed-industries/zed/issues/4577,
https://github.com/zed-industries/zed/issues/21697,
https://github.com/zed-industries/zed/issues/26901#issuecomment-2737485096

Todo:

- [x] Test case when extension is installed, does vtsls workspace config
refreshes?

Before:
<img width="450" alt="image"
src="https://github.com/user-attachments/assets/f242167c-5264-44ab-b5a7-8c90eb75c6a1"
/>

After:
<img width="450" alt="image"
src="https://github.com/user-attachments/assets/6a5f1afe-a0e1-4f64-8a95-919b0bf97614"
/>

Release Notes:

- N/A

crates/language/src/language.rs

@@ -305,6 +305,7 @@ pub trait LspAdapterDelegate: Send + Sync {
     fn worktree_root_path(&self) -> &Path;
     fn exists(&self, path: &Path, is_dir: Option<bool>) -> bool;
     fn update_status(&self, language: LanguageServerName, status: BinaryStatus);
+    fn registered_lsp_adapters(&self) -> Vec<Arc<dyn LspAdapter>>;
     async fn language_server_download_dir(&self, name: &LanguageServerName) -> Option<Arc<Path>>;
 
     async fn npm_package_installed_version(
@@ -515,6 +516,26 @@ pub trait LspAdapter: 'static + Send + Sync {
         Ok(serde_json::json!({}))
     }
 
+    async fn additional_initialization_options(
+        self: Arc<Self>,
+        _target_language_server_id: LanguageServerName,
+        _: &dyn Fs,
+        _: &Arc<dyn LspAdapterDelegate>,
+    ) -> Result<Option<Value>> {
+        Ok(None)
+    }
+
+    async fn additional_workspace_configuration(
+        self: Arc<Self>,
+        _target_language_server_id: LanguageServerName,
+        _: &dyn Fs,
+        _: &Arc<dyn LspAdapterDelegate>,
+        _: Arc<dyn LanguageToolchainStore>,
+        _cx: &mut AsyncApp,
+    ) -> Result<Option<Value>> {
+        Ok(None)
+    }
+
     /// Returns a list of code actions supported by a given LspAdapter
     fn code_action_kinds(&self) -> Option<Vec<CodeActionKind>> {
         Some(vec![

crates/language/src/language_registry.rs

@@ -912,6 +912,15 @@ impl LanguageRegistry {
             .unwrap_or_default()
     }
 
+    pub fn all_lsp_adapters(&self) -> Vec<Arc<CachedLspAdapter>> {
+        self.state
+            .read()
+            .all_lsp_adapters
+            .values()
+            .cloned()
+            .collect()
+    }
+
     pub fn adapter_for_name(&self, name: &LanguageServerName) -> Option<Arc<CachedLspAdapter>> {
         self.state.read().all_lsp_adapters.get(name).cloned()
     }