git: Enable git stash in git panel (#32821)

Related discussion #31484

Release Notes:

- Added a menu entry on the git panel to git stash and git pop stash. 

Preview: 


![Screenshot-2025-06-17_08:26:36](https://github.com/user-attachments/assets/d3699ba4-511f-4c7b-a7cc-00a295d01f64)

---------

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

crates/proto/src/proto.rs

@@ -261,6 +261,8 @@ messages!(
     (Unfollow, Foreground),
     (UnshareProject, Foreground),
     (Unstage, Background),
+    (Stash, Background),
+    (StashPop, Background),
     (UpdateBuffer, Foreground),
     (UpdateBufferFile, Foreground),
     (UpdateChannelBuffer, Foreground),
@@ -419,6 +421,8 @@ request_messages!(
     (TaskContextForLocation, TaskContext),
     (Test, Test),
     (Unstage, Ack),
+    (Stash, Ack),
+    (StashPop, Ack),
     (UpdateBuffer, Ack),
     (UpdateParticipantLocation, Ack),
     (UpdateProject, Ack),
@@ -549,6 +553,8 @@ entity_messages!(
     TaskContextForLocation,
     UnshareProject,
     Unstage,
+    Stash,
+    StashPop,
     UpdateBuffer,
     UpdateBufferFile,
     UpdateDiagnosticSummary,