git: Pick which remote to fetch (#26897)

I don't want to fetch `--all` branch, we should can picker which remote
to fetch.

Release Notes:

- Added the `git::FetchFrom` action to fetch from a single remote.

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

crates/proto/proto/git.proto

@@ -326,6 +326,7 @@ message Fetch {
     reserved 2;
     uint64 repository_id = 3;
     uint64 askpass_id = 4;
+    optional string remote = 5;
 }
 
 message GetRemotes {