assistant2: Add initial concept of profiles (#27123)

This PR adds the initial concept of agent profiles to Assistant 2.

Right now these are just collections of tools that can quickly be
enabled together:


https://github.com/user-attachments/assets/7c7f9cc8-a5e5-492f-96f7-79697bbf3d72

There are currently two profiles:

- `Read-only` - Consists only of tools that do not perform writes.
- `Code Writer` - Consists of all tools for writing code, with the
exception of the `lua-interpreter`.

Release Notes:

- N/A

crates/assistant2/src/assistant.rs

@@ -1,4 +1,5 @@
 mod active_thread;
+mod agent_profile;
 mod assistant_configuration;
 mod assistant_model_selector;
 mod assistant_panel;