vc4/ci: switch to test on arm64

So far we were running VC4 tests in arm32 because that Raspberry PI OS 32-bits was the suggested version for rpi3.

But nowadays, the suggested version is 64-bits, for rpi3 and newers. So it makes sense to move the jobs to run in 32-bits, like in rpi4 and rpi5.

Still, for devices like rpi1 and rpi2, the suggested flavour is still 32-bits. And also, users can still decide to go with the 32-bit version.

Hence, we add a couple of nightly jobs to run the OpenGL/ES CTS tests in 32-bits, for vc4 and v3d (we don't include Vulkan because the 32-bit container don't have Vulkan). These jobs runs a subset of the tests, so they will finish in less than the standard time, 20 min.