bcachefs: Option changes now get propagated to reflinked data

bcachefs: Option changes now get propagated to reflinked data

Now that bch2_move_get_io_opts() re-propagates changed inode io options
to bch_extent_rebalance, we can properly suport changing IO path options
for reflinked data.

Changing a per-file IO path option, either via the xattr interface or
via the BCHFS_IOC_REINHERIT_ATTRS ioctl, will now trigger a scan (the
inode number is marked as needing a scan, via
bch2_set_rebalance_needs_scan()), and rebalance will use
bch2_move_data(), which will walk the inode number and pick up the new
options.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>