Make git blame for SSH remote projects (#15106)

This also refactors the BufferStore + WorktreeStore interfaces to make
them cleaner, more fully encapsulating the RPC aspects of their
functionality.

Release Notes:

- N/A

crates/proto/src/proto.rs

@@ -103,6 +103,10 @@ impl AnyProtoClient {
         let envelope = request.into_envelope(0, None, None);
         self.0.send(envelope)
     }
+
+    pub fn send_dynamic(&self, message: Envelope) -> anyhow::Result<()> {
+        self.0.send(message)
+    }
 }
 
 impl<T: EnvelopedMessage> AnyTypedEnvelope for TypedEnvelope<T> {