Add Luau-style ref paths migration plan and update related tests

- Introduced a new migration plan for converting `Rojo_Ref_*` attribute paths to Luau require-by-string style, enhancing portability with relative paths.
- Updated existing test snapshots to reflect the new path formats, ensuring consistency across various scenarios.
- Enhanced the `compute_relative_ref_path` and `resolve_ref_path` functions to support the new path semantics, improving path resolution logic.
- Refactored related code in `change_processor`, `syncback`, and `snapshot` modules to accommodate the new reference path handling.

These changes improve the robustness and maintainability of reference path management in the project.

rojo-test/serve-test-snapshots/end_to_end__tests__serve__ref_path_change_target_patch.snap

@@ -15,7 +15,7 @@ body:
             Attributes:
               "!Attributes":
                 Rojo_Ref_PrimaryPart:
-                  "!String": Workspace/MyModel/OtherPart
+                  "!String": "@self/OtherPart"
             PrimaryPart:
               "!Ref": id-4
           id: id-3

rojo-test/serve-test-snapshots/end_to_end__tests__serve__ref_path_multiple_attrs_patch.snap

@@ -15,9 +15,9 @@ body:
             Attributes:
               "!Attributes":
                 Rojo_Ref_CustomRef:
-                  "!String": Workspace/MyModel/OtherPart
+                  "!String": "@self/OtherPart"
                 Rojo_Ref_PrimaryPart:
-                  "!String": Workspace/MyModel/Target
+                  "!String": "@self/Target"
             CustomRef:
               "!Ref": id-4
           id: id-3

rojo-test/serve-test-snapshots/end_to_end__tests__serve__ref_path_new_file_patch.snap

@@ -28,7 +28,7 @@ body:
             Attributes:
               "!Attributes":
                 Rojo_Ref_PrimaryPart:
-                  "!String": Workspace/MyModel/Target
+                  "!String": "@self/Target"
           id: id-3
 packetType: messages
 sessionId: id-1

rojo-test/serve-test-snapshots/end_to_end__tests__serve__ref_path_nonexistent_patch.snap

@@ -15,7 +15,7 @@ body:
             Attributes:
               "!Attributes":
                 Rojo_Ref_PrimaryPart:
-                  "!String": Workspace/NonExistent/Part
+                  "!String": "./NonExistent/Part"
             PrimaryPart: ~
           id: id-3
 packetType: messages

rojo-test/serve-tests/ref_forward_sync/src/Workspace/MyModel/init.meta.json5

@@ -1,6 +1,6 @@
 {
   "className": "Model",
   "attributes": {
-    "Rojo_Ref_PrimaryPart": "Workspace/MyModel/Target"
+    "Rojo_Ref_PrimaryPart": "@self/Target"
   }
 }

rojo-test/serve-tests/ref_two_way_sync/src/Workspace/TestModel/init.meta.json5

@@ -1,6 +1,6 @@
 {
   "className": "Model",
   "attributes": {
-    "Rojo_Ref_PrimaryPart": "Workspace/TestModel/Part1.model.json5"
+    "Rojo_Ref_PrimaryPart": "@self/Part1.model.json5"
   }
 }

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__duplicate_rojo_id-container.model.json5.snap

@@ -7,7 +7,7 @@ expression: container.model.json5
     {
       attributes: {
         Rojo_Id: "value_1",
-        Rojo_Ref_Value: "ReplicatedStorage/container/value_1.model.json5"
+        Rojo_Ref_Value: "@self"
       },
       className: "ObjectValue",
       name: "value_1"
@@ -15,7 +15,7 @@ expression: container.model.json5
     {
       attributes: {
         Rojo_Id: "value_1",
-        Rojo_Ref_Value: "ReplicatedStorage/container/value_2.model.json5"
+        Rojo_Ref_Value: "@self"
       },
       className: "ObjectValue",
       name: "value_2"

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__ref_properties-src__pointer.model.json5.snap

@@ -4,7 +4,7 @@ expression: src/pointer.model.json5
 ---
 {
   attributes: {
-    Rojo_Ref_Value: "target.model.json5"
+    Rojo_Ref_Value: "@game/target.model.json5"
   },
   className: "ObjectValue"
 }

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__ref_properties_blank-src__pointer.model.json5.snap

@@ -4,7 +4,7 @@ expression: src/pointer.model.json5
 ---
 {
   attributes: {
-    Rojo_Ref_Value: "target.txt"
+    Rojo_Ref_Value: "@game/target.txt"
   },
   className: "ObjectValue"
 }

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__ref_properties_conflict-src__Pointer_2.model.json5.snap

@@ -4,7 +4,7 @@ expression: src/Pointer_2.model.json5
 ---
 {
   attributes: {
-    Rojo_Ref_Value: "Target_2.model.json5"
+    Rojo_Ref_Value: "@game/Target_2.model.json5"
   },
   className: "ObjectValue"
 }

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__ref_properties_pruned-src__Pointer1.model.json5.snap

@@ -4,7 +4,7 @@ expression: src/Pointer1.model.json5
 ---
 {
   attributes: {
-    Rojo_Ref_Value: "ReplicatedStorage/Target1.model.json5"
+    Rojo_Ref_Value: "@game/ReplicatedStorage/Target1.model.json5"
   },
   className: "ObjectValue"
 }

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__ref_properties_pruned-src__Pointer2.model.json5.snap

@@ -4,7 +4,7 @@ expression: src/Pointer2.model.json5
 ---
 {
   attributes: {
-    Rojo_Ref_Value: "ReplicatedStorage/Target2.model.json5"
+    Rojo_Ref_Value: "@game/ReplicatedStorage/Target2.model.json5"
   },
   className: "ObjectValue"
 }

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__ref_properties_pruned-src__Pointer3.model.json5.snap

@@ -4,7 +4,7 @@ expression: src/Pointer3.model.json5
 ---
 {
   attributes: {
-    Rojo_Ref_Value: "ReplicatedStorage/Target3.model.json5"
+    Rojo_Ref_Value: "@game/ReplicatedStorage/Target3.model.json5"
   },
   className: "ObjectValue"
 }

rojo-test/syncback-tests/UFOWave_matching/expected/Hitbox/Water.model.json5

@@ -1,6 +1,6 @@
 {
   attributes: {
-    Rojo_Ref_SoundGroup: "ServerStorage/__server_muted.model.json5"
+    Rojo_Ref_SoundGroup: "../../__server_muted.model.json5"
   },
   className: "Sound",
   properties: {

rojo-test/syncback-tests/UFOWave_matching/expected/init.meta.json5

@@ -1,6 +1,6 @@
 {
   attributes: {
-    Rojo_Ref_PrimaryPart: "ServerStorage/UFOWave/TsunamiWave",
+    Rojo_Ref_PrimaryPart: "@self/TsunamiWave",
     Speed: 10,
     ZonesPassed: {
       Float32: 0