Add git branch switching aliases (#26315)

This gives us _very_ rudimentary support for `git switch` and `git
checkout` now, by making them aliases for our existing `git::branch`
call.

Release Notes:

- Git Beta: Added `git::Switch` and `git::CheckoutBranch` as aliases for
the existing `git::Branch`

crates/zed_actions/src/lib.rs

@@ -114,8 +114,9 @@ pub mod workspace {
 }
 
 pub mod git {
-    use gpui::action_with_deprecated_aliases;
+    use gpui::{action_with_deprecated_aliases, actions};
 
+    actions!(git, [CheckoutBranch, Switch]);
     action_with_deprecated_aliases!(git, Branch, ["branches::OpenRecent"]);
 }