gl_rasterizer_cache: Use std::vector::assign in LoadGLBuffer() for the non-tiled case

resize() causes the vector to expand and zero out the added members to
the vector, however we can avoid this zeroing by using assign().

Given we have the pointer to the data we want to copy, we can calculate
the end pointer and directly copy the range of data without the
need to perform the resize() beforehand.

src/video_core/renderer_opengl/gl_rasterizer_cache.cpp

@@ -451,16 +451,18 @@ void CachedSurface::LoadGLBuffer() {
 
     ASSERT(texture_src_data);
 
-    gl_buffer.resize(params.width * params.height * GetGLBytesPerPixel(params.pixel_format));
+    const u32 bytes_per_pixel = GetGLBytesPerPixel(params.pixel_format);
+    const u32 copy_size = params.width * params.height * bytes_per_pixel;
 
     MICROPROFILE_SCOPE(OpenGL_SurfaceLoad);
 
     if (!params.is_tiled) {
-        const u32 bytes_per_pixel{params.GetFormatBpp() >> 3};
+        const u8* const texture_src_data_end = texture_src_data + copy_size;
 
-        std::memcpy(gl_buffer.data(), texture_src_data,
-                    bytes_per_pixel * params.width * params.height);
+        gl_buffer.assign(texture_src_data, texture_src_data_end);
     } else {
+        gl_buffer.resize(copy_size);
+
         morton_to_gl_fns[static_cast<size_t>(params.pixel_format)](
             params.width, params.block_height, params.height, gl_buffer.data(), params.addr);
     }