Verify Qt Quick and Quick 3D with QRhi on Embedded Linux (and CMake)

With the default OpenGL code path being removed in Qt 6.0, all platforms and devices that are not verified with the new QRhi-based rendering path become unsupported by default.

To not end up in regression hell, the bare minimum in the embedded (Linux) space is to test, measure, and fix if needed the following:

• Raspberry Pi 4 with new Mesa V3D stack (OpenGL ES 3.0 only), OpenGL backend. Both X11 and eglfs on eglfs_kms.

• Raspberry Pi 3 with old Broadcom stack (OpenGL ES 2.0 only), OpenGL backend. (eglfs on eglfs_brcm)

• i.MX8 (Vivante, GLES 3.2? what about Vulkan here?)

• i.MX6 (Vivante, GLES 3.0, eglfs on eglfs_viv)

• Jetson TX2 (Linux, GLES, Vulkan)