feat: Assign texture format value to RenderTarget[Cube]Texture

src/Engine/babylon.engine.ts

@@ -4879,6 +4879,7 @@
             texture.generateMipMaps = fullOptions.generateMipMaps ? true : false;
             texture.samplingMode = fullOptions.samplingMode;
             texture.type = fullOptions.type;
+            texture.format = fullOptions.format;
             texture._generateDepthBuffer = fullOptions.generateDepthBuffer;
             texture._generateStencilBuffer = fullOptions.generateStencilBuffer ? true : false;
 
@@ -5382,6 +5383,7 @@
             texture.generateMipMaps = fullOptions.generateMipMaps;
             texture.samplingMode = fullOptions.samplingMode;
             texture.type = fullOptions.type;
+            texture.format = fullOptions.format;
             texture._generateDepthBuffer = fullOptions.generateDepthBuffer;
             texture._generateStencilBuffer = fullOptions.generateStencilBuffer;