Simplify proto::Buffer to express its fields in terms of operations

crates/rpc/proto/zed.proto

@@ -813,11 +813,7 @@ message Buffer {
     optional File file = 2;
     string base_text = 3;
     repeated Operation operations = 4;
-    repeated SelectionSet selections = 5;
-    repeated Diagnostic diagnostics = 6;
-    uint32 diagnostics_timestamp = 7;
-    repeated string completion_triggers = 8;
-    LineEnding line_ending = 9;
+    LineEnding line_ending = 5;
 }
 
 enum LineEnding {

crates/rpc/src/rpc.rs

@@ -6,4 +6,4 @@ pub use conn::Connection;
 pub use peer::*;
 mod macros;
 
-pub const PROTOCOL_VERSION: u32 = 30;
+pub const PROTOCOL_VERSION: u32 = 31;