Use different commit author for collab project clients (#24058)

Follow-up of https://github.com/zed-industries/zed/pull/23869

* Retrieves user + email for collab project clients and use these when
such users commit

Same as in https://github.com/zed-industries/zed/pull/23329, "is it the
right user name and e-mail" and "how to override these" questions apply.

* If this data is unavailable, forbid committing to the remote client

* Forbid running related actions in git panel, if committing/writing is
not permitted


Release Notes:

- N/A

crates/call/src/cross_platform/room.rs

@@ -532,6 +532,10 @@ impl Room {
         &self.local_participant
     }
 
+    pub fn local_participant_user(&self, cx: &App) -> Option<Arc<User>> {
+        self.user_store.read(cx).current_user()
+    }
+
     pub fn remote_participants(&self) -> &BTreeMap<u64, RemoteParticipant> {
         &self.remote_participants
     }

crates/call/src/macos/room.rs

@@ -588,6 +588,10 @@ impl Room {
         &self.local_participant
     }
 
+    pub fn local_participant_user(&self, cx: &App) -> Option<Arc<User>> {
+        self.user_store.read(cx).current_user()
+    }
+
     pub fn remote_participants(&self) -> &BTreeMap<u64, RemoteParticipant> {
         &self.remote_participants
     }