enable-resume (#3537)

Adding the ability to resume conversations.
we have one verb `resume`. 

Behavior:

`tui`:
`codex resume`: opens session picker
`codex resume --last`: continue last message
`codex resume <session id>`: continue conversation with `session id`

`exec`:
`codex resume --last`: continue last conversation
`codex resume <session id>`: continue conversation with `session id`

Implementation:
- I added a function to find the path in `~/.codex/sessions/` with a
`UUID`. This is helpful in resuming with session id.
- Added the above mentioned flags
- Added lots of testing

codex-rs/core/src/rollout/mod.rs

@@ -8,6 +8,7 @@ pub(crate) mod policy;
 pub mod recorder;
 
 pub use codex_protocol::protocol::SessionMeta;
+pub use list::find_conversation_path_by_id_str;
 pub use recorder::RolloutRecorder;
 pub use recorder::RolloutRecorderParams;