fixing URP UniversalResourceData resource setters that should not be public

Fixing URP frame resource setters that should not be public. This avoids many kinds of user errors and bugs due to unexpected behavior. It also minimizes the issue of frame resource handles and global texture reference becoming out-of-sync. This is a partial fix to https://jira.unity3d.com/browse/UUM-69948

This is new API that landed in 23.3 but that accidently made setters public that should not be, since it's incorrect user behavior to set these. This PR adds guardrails to guide users better. Since this is new API, and a very advanced use case, this should only impact a handful of users at most.

Author: UnityAljosha

Packages/com.unity.render-pipelines.universal/Runtime/FrameData/UniversalResourceData.cs

@@ -89,7 +89,7 @@ public bool isActiveTargetBackBuffer
         public TextureHandle backBufferColor
         {
             get => CheckAndGetTextureHandle(ref _backBufferColor);
-            set => CheckAndSetTextureHandle(ref _backBufferColor, value);
+            internal set => CheckAndSetTextureHandle(ref _backBufferColor, value);
         }
         private TextureHandle _backBufferColor;
 
@@ -100,7 +100,7 @@ public TextureHandle backBufferColor
         public TextureHandle backBufferDepth
         {
             get => CheckAndGetTextureHandle(ref _backBufferDepth);
-            set => CheckAndSetTextureHandle(ref _backBufferDepth, value);
+            internal set => CheckAndSetTextureHandle(ref _backBufferDepth, value);
         }
         private TextureHandle _backBufferDepth;
 
@@ -170,7 +170,7 @@ public TextureHandle[] gBuffer
         public TextureHandle cameraOpaqueTexture
         {
             get => CheckAndGetTextureHandle(ref _cameraOpaqueTexture);
-            set => CheckAndSetTextureHandle(ref _cameraOpaqueTexture, value);
+            internal set => CheckAndSetTextureHandle(ref _cameraOpaqueTexture, value);
         }
         private TextureHandle _cameraOpaqueTexture;
 
@@ -180,7 +180,7 @@ public TextureHandle cameraOpaqueTexture
         public TextureHandle cameraDepthTexture
         {
             get => CheckAndGetTextureHandle(ref _cameraDepthTexture);
-            set => CheckAndSetTextureHandle(ref _cameraDepthTexture, value);
+            internal set => CheckAndSetTextureHandle(ref _cameraDepthTexture, value);
         }
         private TextureHandle _cameraDepthTexture;
 
@@ -190,7 +190,7 @@ public TextureHandle cameraDepthTexture
         public TextureHandle cameraNormalsTexture
         {
             get => CheckAndGetTextureHandle(ref _cameraNormalsTexture);
-            set => CheckAndSetTextureHandle(ref _cameraNormalsTexture, value);
+            internal set => CheckAndSetTextureHandle(ref _cameraNormalsTexture, value);
         }
         private TextureHandle _cameraNormalsTexture;
 
@@ -257,7 +257,7 @@ internal TextureHandle debugScreenDepth
         public TextureHandle afterPostProcessColor
         {
             get => CheckAndGetTextureHandle(ref _afterPostProcessColor);
-            set => CheckAndSetTextureHandle(ref _afterPostProcessColor, value);
+            internal set => CheckAndSetTextureHandle(ref _afterPostProcessColor, value);
         }
         private TextureHandle _afterPostProcessColor;
 
@@ -267,7 +267,7 @@ public TextureHandle afterPostProcessColor
         public TextureHandle overlayUITexture
         {
             get => CheckAndGetTextureHandle(ref _overlayUITexture);
-            set => CheckAndSetTextureHandle(ref _overlayUITexture, value);
+            internal set => CheckAndSetTextureHandle(ref _overlayUITexture, value);
         }
         private TextureHandle _overlayUITexture;
 
@@ -279,7 +279,7 @@ public TextureHandle overlayUITexture
         public TextureHandle renderingLayersTexture
         {
             get => CheckAndGetTextureHandle(ref _renderingLayersTexture);
-            set => CheckAndSetTextureHandle(ref _renderingLayersTexture, value);
+            internal set => CheckAndSetTextureHandle(ref _renderingLayersTexture, value);
         }
         private TextureHandle _renderingLayersTexture;
 
@@ -311,7 +311,7 @@ public TextureHandle dBufferDepth
         public TextureHandle ssaoTexture
         {
             get => CheckAndGetTextureHandle(ref _ssaoTexture);
-            set => CheckAndSetTextureHandle(ref _ssaoTexture, value);
+            internal set => CheckAndSetTextureHandle(ref _ssaoTexture, value);
         }
         private TextureHandle _ssaoTexture;