Add auto-masking as a popover in the header while in Sculpt mode,
following the design in T101593.
These properties were present in the Options panel (and popover),
they have been removed from there.
Moreover, this commit makes the auto-masking section in Brush settings
match the new popover.
In the future this popover can be used for other modes that support
auto-masking such as Grease Pencil.
See D16145 for details and screenshots.
Reviewed By: JulienKaspar
Differential Revision: https://developer.blender.org/D16145
db40b62252