Merge netfs API documentation updates

Bring in the netfs API documentation updates which had been in the
vfs-6.16.misc branch for most of this cycle. So don't needlessly rewrite
the vfs-6.16.misc by dropping it from that branch and moving it to
vfs-6.16.netfs. Simply merge vfs-6.16.misc into vfs-6.16.netfs.

Signed-off-by: Christian Brauner <brauner@kernel.org>