We ignored assertions happening on callbacks as they only raise
exceptions that does not stop the execution.
So ensure that this is happening in all the tests as synaptics was
doing already
It can be convenient for device users to check what it supports, without
having multiple functions to check each single feature.
So expose this and add tests.
The code tried to only write the RGB bytes of FORMAT_RGB24, however, the
in-memory layout is different on big-endian which would result in the
wrong bytes being written.
Fix this by simply also writing the byte we do not care about.
