When running RenderPerf on 3D tests (3DSphere, 3DCylinder) memory usage continuously increases on D3D12. Potentially there's a memory leak that also might lower performance in those tests - investigate and fix.

Similar behavior is seen in Button test, which uses lots of Texture update calls.

To reproduce (assumes RenderPerfTest is in renderperf directory):
```
java @<jfx_dir>/build/run.args -Djavafx.animation.fullspeed=true -Dprism.order=d3d12 renderperf.RenderPerfTest -n 10000 -t 3DSphere
```