This commit moves the freestyle edge and face mark tags to become
generic attributes, similar to other changes over the past years. The
attributes are called "freestyle_edge" and "freestyle_face", and they're
now propagated like regular boolean attributes.
Compatibility wise, forward and backward blend file compatibility are
maintained (for forward compatibility this is implemented a bit
differently than in the past because of the ongoing `AttributeStorage`
transition). In the Python API, `use_freestyle_mark` has been removed;
the attribute API should be used instead (just like bevel weights).
The BMesh (`freestyle`) accessors are removed too.
The conversions benefit from the fact that bit-wise, the old structs are
the same as `bool`, so we can convert to the old and new formats without
reallocating arrays.
Pull Request: https://projects.blender.org/blender/blender/pulls/141996
b20ecee555