In wlr_drm_format_dup, allocate the new wlr_drm_format using cap instead
of len. This makes it so the cap field is up-to-date and the chunk of
memory isn't too small if we append new modifiers (we don't allow this
yet but might in the future).
This types adds a container for formats + modifiers.
A list that is of [format [modifier]] was chosen instead of
[format modifer] because that is how GBM accepts them.
Co-Authored-By: emersion <contact@emersion.fr>
