Add Code Symbols tool (#27733)

Lets you get all the code symbols in the project (like the Code Symbols
panel) or in a particular file (like the Outline panel), optionally
paginated and filtering results by regex. The tool gives the files,
lines, and numbers of all of these, which means they can be used in
conjunction with the read file tool to read subsets of large files
without having to open the entire large file and poke around in it.

<img width="621" alt="Screenshot 2025-03-29 at 12 00 21 PM"
src="https://github.com/user-attachments/assets/d78259d7-2746-44c0-ac18-2e21f2505c0a"
/>

Release Notes:

- N/A

crates/assistant_tools/src/assistant_tools.rs

@@ -1,5 +1,7 @@
 mod bash_tool;
 mod batch_tool;
+mod code_symbol_iter;
+mod code_symbols_tool;
 mod copy_path_tool;
 mod create_directory_tool;
 mod create_file_tool;
@@ -29,6 +31,7 @@ use move_path_tool::MovePathTool;
 
 use crate::bash_tool::BashTool;
 use crate::batch_tool::BatchTool;
+use crate::code_symbols_tool::CodeSymbolsTool;
 use crate::create_directory_tool::CreateDirectoryTool;
 use crate::create_file_tool::CreateFileTool;
 use crate::delete_path_tool::DeletePathTool;
@@ -64,6 +67,7 @@ pub fn init(http_client: Arc<HttpClientWithUrl>, cx: &mut App) {
     registry.register_tool(ListDirectoryTool);
     registry.register_tool(NowTool);
     registry.register_tool(OpenTool);
+    registry.register_tool(CodeSymbolsTool);
     registry.register_tool(PathSearchTool);
     registry.register_tool(ReadFileTool);
     registry.register_tool(RegexSearchTool);