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/extension/src/extension.rs

@@ -76,6 +76,20 @@ pub trait Extension: Send + Sync + 'static {
         worktree: Arc<dyn WorktreeDelegate>,
     ) -> Result<Option<String>>;
 
+    async fn language_server_additional_initialization_options(
+        &self,
+        language_server_id: LanguageServerName,
+        target_language_server_id: LanguageServerName,
+        worktree: Arc<dyn WorktreeDelegate>,
+    ) -> Result<Option<String>>;
+
+    async fn language_server_additional_workspace_configuration(
+        &self,
+        language_server_id: LanguageServerName,
+        target_language_server_id: LanguageServerName,
+        worktree: Arc<dyn WorktreeDelegate>,
+    ) -> Result<Option<String>>;
+
     async fn labels_for_completions(
         &self,
         language_server_id: LanguageServerName,