Git context menu (#24844)

Adds the non-entry specific right click menu to the panel, and the
features contained therin:

* Stage all
* Discard Tracked Changes
* Trash Untracked Files

Also changes the naming from "Changes"/"New" to better match Git's
terminology (though not convinced on this, it was awkward to describe
"Discard Changes" without a way to distinguish between the changes and
the files containing them).

Release Notes:

- N/A

crates/proto/proto/zed.proto

@@ -320,7 +320,8 @@ message Envelope {
         GitReset git_reset = 301;
         GitCommitDetails git_commit_details = 302;
 
-        SetIndexText set_index_text = 299; // current max
+        SetIndexText set_index_text = 299;
+        GitCheckoutFiles git_checkout_files = 303; // current max
     }
 
     reserved 87 to 88;
@@ -2688,6 +2689,14 @@ message GitReset {
     }
 }
 
+message GitCheckoutFiles {
+    uint64 project_id = 1;
+    uint64 worktree_id = 2;
+    uint64 work_directory_id = 3;
+    string commit = 4;
+    repeated string paths = 5;
+}
+
 message GetPanicFilesResponse {
     repeated string file_contents = 2;
 }

crates/proto/src/proto.rs

@@ -441,6 +441,7 @@ messages!(
     (InstallExtension, Background),
     (RegisterBufferWithLanguageServers, Background),
     (GitReset, Background),
+    (GitCheckoutFiles, Background),
     (GitShow, Background),
     (GitCommitDetails, Background),
     (SetIndexText, Background),
@@ -579,6 +580,7 @@ request_messages!(
     (RegisterBufferWithLanguageServers, Ack),
     (GitShow, GitCommitDetails),
     (GitReset, Ack),
+    (GitCheckoutFiles, Ack),
     (SetIndexText, Ack),
 );
 
@@ -674,6 +676,7 @@ entity_messages!(
     RegisterBufferWithLanguageServers,
     GitShow,
     GitReset,
+    GitCheckoutFiles,
     SetIndexText,
 );