Our wlr_format_set structs don't hold GBM usage flags. Instead, users
who want to get a LINEAR buffer can use the DRM_FORMAT_MOD_LINEAR
modifier even if the kernel driver doesn't support modifiers.
Add a special case to wlr_drm_format_intersect to properly handle this
situation.
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>
