debugger: Start work on adding session snapshot feature (#44298)

This PR adds the basic logic for a feature that allows you to visit any
stopped information back in time. We will follow up with PRs to improve
this and actually add UI for it so the UX is better.


https://github.com/user-attachments/assets/42d8a5b3-8ab8-471a-bdd0-f579662eadd6


Edit Anthony:

We feature flagged this so external users won't be able to access this
until the feature is polished

Release Notes:

- N/A

---------

Co-authored-by: Anthony Eid <hello@anthonyeid.me>

crates/debugger_ui/src/session/running.rs

@@ -1743,7 +1743,7 @@ impl RunningState {
 
         let is_building = self.session.update(cx, |session, cx| {
             session.shutdown(cx).detach();
-            matches!(session.mode, session::SessionState::Booting(_))
+            matches!(session.state, session::SessionState::Booting(_))
         });
 
         if is_building {