Fixes to commit button in Git Panel (#24425)

Git Panel updates:

* Fixes commit/commit all button to work (and be disabled correctly in
merge conflict status)
* Updates keyboard shortcuts and sets focus on the button (enter now
does the same as click; tab cycles between editor and change list)


Closes #ISSUE

Release Notes:

- N/A *or* Added/Fixed/Improved ...

---------

Co-authored-by: Cole Miller <cole@zed.dev>

crates/git/src/git.rs

@@ -38,8 +38,7 @@ actions!(
         StageAll,
         UnstageAll,
         RevertAll,
-        CommitChanges,
-        CommitAllChanges,
+        Commit,
         ClearCommitMessage
     ]
 );