fusefs: implement FUSE_NO_OPEN_SUPPORT and FUSE_NO_OPENDIR_SUPPORT

For file systems that allow it, fusefs will skip FUSE_OPEN,
FUSE_RELEASE, FUSE_OPENDIR, and FUSE_RELEASEDIR operations, a minor
optimization.

MFC after: 2 weeks
Reviewed by: pfg
Differential Revision: https://reviews.freebsd.org/D32141