QRenderCapture leaks memory with RHI renderer

Memory leak when capturing using QRenderCapture with RHI renderer.

Steps to reproduce:

1. Apply the patch https://codereview.qt-project.org/c/qt/qt3d/+/434078
2. build and run qt3d/tests/manual/rendercapture-qml
3. check 'continuous' and push 'Render Capture'

Memory usage increases gradually.

No memory leaks with OpenGL renderer.

Based on Visual Studio's analysis tools, the primary instance of the leak appears to be the instance of QD3D11ShaderResourceBindings created by the QRhiD3D11::createShaderResourceBindings() function.
This is deleted in the RHIPipelineBase::cleanup function, which is only called when the application exits.