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/proto/proto/zed.proto

@@ -2656,4 +2656,6 @@ message Commit {
     uint64 worktree_id = 2;
     uint64 work_directory_id = 3;
     string message = 4;
+    optional string name = 5;
+    optional string email = 6;
 }