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_api/src/extension_api.rs

@@ -93,6 +93,26 @@ pub trait Extension: Send + Sync {
         Ok(None)
     }
 
+    /// Returns the initialization options to pass to the other language server.
+    fn language_server_additional_initialization_options(
+        &mut self,
+        _language_server_id: &LanguageServerId,
+        _target_language_server_id: &LanguageServerId,
+        _worktree: &Worktree,
+    ) -> Result<Option<serde_json::Value>> {
+        Ok(None)
+    }
+
+    /// Returns the workspace configuration options to pass to the other language server.
+    fn language_server_additional_workspace_configuration(
+        &mut self,
+        _language_server_id: &LanguageServerId,
+        _target_language_server_id: &LanguageServerId,
+        _worktree: &Worktree,
+    ) -> Result<Option<serde_json::Value>> {
+        Ok(None)
+    }
+
     /// Returns the label for the given completion.
     fn label_for_completion(
         &self,
@@ -235,6 +255,38 @@ impl wit::Guest for Component {
             .and_then(|value| serde_json::to_string(&value).ok()))
     }
 
+    fn language_server_additional_initialization_options(
+        language_server_id: String,
+        target_language_server_id: String,
+        worktree: &Worktree,
+    ) -> Result<Option<String>, String> {
+        let language_server_id = LanguageServerId(language_server_id);
+        let target_language_server_id = LanguageServerId(target_language_server_id);
+        Ok(extension()
+            .language_server_additional_initialization_options(
+                &language_server_id,
+                &target_language_server_id,
+                worktree,
+            )?
+            .and_then(|value| serde_json::to_string(&value).ok()))
+    }
+
+    fn language_server_additional_workspace_configuration(
+        language_server_id: String,
+        target_language_server_id: String,
+        worktree: &Worktree,
+    ) -> Result<Option<String>, String> {
+        let language_server_id = LanguageServerId(language_server_id);
+        let target_language_server_id = LanguageServerId(target_language_server_id);
+        Ok(extension()
+            .language_server_additional_workspace_configuration(
+                &language_server_id,
+                &target_language_server_id,
+                worktree,
+            )?
+            .and_then(|value| serde_json::to_string(&value).ok()))
+    }
+
     fn labels_for_completions(
         language_server_id: String,
         completions: Vec<Completion>,