Editor: support go to implementation (#7890)

Release Notes:

- Added "Go to implementation" support in editor.

crates/rpc/proto/zed.proto

@@ -12,6 +12,14 @@ message Envelope {
     uint32 id = 1;
     optional uint32 responding_to = 2;
     optional PeerId original_sender_id = 3;
+    
+    /*
+        When you are adding a new message type, instead of adding it in semantic order
+        and bumping the message ID's of everything that follows, add it at the end of the
+        file and bump the max number. See this
+        https://github.com/zed-industries/zed/pull/7890#discussion_r1496621823
+
+    */
     oneof payload {
         Hello hello = 4;
         Ack ack = 5;
@@ -48,6 +56,7 @@ message Envelope {
         GetDefinitionResponse get_definition_response = 33;
         GetTypeDefinition get_type_definition = 34;
         GetTypeDefinitionResponse get_type_definition_response = 35;
+        
         GetReferences get_references = 36;
         GetReferencesResponse get_references_response = 37;
         GetDocumentHighlights get_document_highlights = 38;
@@ -183,7 +192,10 @@ message Envelope {
         LspExtExpandMacroResponse lsp_ext_expand_macro_response = 155;
         SetRoomParticipantRole set_room_participant_role = 156;
 
-        UpdateUserChannels update_user_channels = 157;
+        UpdateUserChannels update_user_channels = 157; 
+
+        GetImplementation get_implementation = 162;
+        GetImplementationResponse get_implementation_response = 163;
     }
 
     reserved 158 to 161;
@@ -503,6 +515,16 @@ message GetTypeDefinition {
 message GetTypeDefinitionResponse {
     repeated LocationLink links = 1;
 }
+message GetImplementation {
+     uint64 project_id = 1;
+     uint64 buffer_id = 2;
+     Anchor position = 3;
+     repeated VectorClockEntry version = 4;
+ }
+
+message GetImplementationResponse {
+    repeated LocationLink links = 1;
+}
 
 message GetReferences {
      uint64 project_id = 1;

crates/rpc/src/proto.rs

@@ -192,6 +192,8 @@ messages!(
     (GetReferencesResponse, Background),
     (GetTypeDefinition, Background),
     (GetTypeDefinitionResponse, Background),
+    (GetImplementation, Background),
+    (GetImplementationResponse, Background),
     (GetUsers, Foreground),
     (Hello, Foreground),
     (IncomingCall, Foreground),
@@ -312,6 +314,7 @@ request_messages!(
     (GetCodeActions, GetCodeActionsResponse),
     (GetCompletions, GetCompletionsResponse),
     (GetDefinition, GetDefinitionResponse),
+    (GetImplementation, GetImplementationResponse),
     (GetDocumentHighlights, GetDocumentHighlightsResponse),
     (GetHover, GetHoverResponse),
     (GetNotifications, GetNotificationsResponse),
@@ -388,6 +391,7 @@ entity_messages!(
     GetCodeActions,
     GetCompletions,
     GetDefinition,
+    GetImplementation,
     GetDocumentHighlights,
     GetHover,
     GetProjectSymbols,