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.

Reviewed by: pfg
Differential Revision: https://reviews.freebsd.org/D32141

(cherry picked from commit 7124d2bc3a3bd58f6d3803a0579f2e0fa853b56d)