git: Add ability to clone remote repositories from Zed (#35606)

This PR adds preliminary git clone support through using the new
`GitClone` action. This works with SSH connections too.

- [x] Get backend working
- [x] Add a UI to interact with this

Future follow-ups:
- Polish the UI
- Have the path select prompt say "Select Repository clone target"
instead of “Open”
- Use Zed path prompt if the user has that as a setting
- Add support for cloning from a user's GitHub repositories directly

Release Notes:

- Add the ability to clone remote git repositories through the `git:
Clone` action

---------

Co-authored-by: hpmcdona <hayden_mcdonald@brown.edu>

crates/proto/src/proto.rs

@@ -316,6 +316,8 @@ messages!(
     (PullWorkspaceDiagnostics, Background),
     (GetDefaultBranch, Background),
     (GetDefaultBranchResponse, Background),
+    (GitClone, Background),
+    (GitCloneResponse, Background)
 );
 
 request_messages!(
@@ -484,6 +486,7 @@ request_messages!(
     (GetDocumentDiagnostics, GetDocumentDiagnosticsResponse),
     (PullWorkspaceDiagnostics, Ack),
     (GetDefaultBranch, GetDefaultBranchResponse),
+    (GitClone, GitCloneResponse)
 );
 
 entity_messages!(
@@ -615,7 +618,8 @@ entity_messages!(
     LogToDebugConsole,
     GetDocumentDiagnostics,
     PullWorkspaceDiagnostics,
-    GetDefaultBranch
+    GetDefaultBranch,
+    GitClone
 );
 
 entity_messages!(