drm_hwcomposer: Virtual display acceleration support

Some platforms like RaspberryPI-4 can benefit from Display Blender IP Core's ability to write back the composition into RAM, offloading the GPU in cases where the display content needs to be used (screen record, remote display, etc.).

To enable this feature the following system property must be enabled:

PRODUCT_VENDOR_PROPERTIES += debug.sf.enable_hwc_vds=1

The feature was requested by the Tesla Android project to improve UI performance.

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