bcachefs: add counter_flags for counters

bcachefs: add counter_flags for counters

In bcachefs, io_read and io_write counter record the amount
of data which has been read and written. They increase in
unit of sector, so to display correctly, they need to be
shifted to the left by the size of a sector. Other counters
like io_move, move_extent_{read, write, finish} also have
this problem.

In order to support different unit, we add extra column to
mark the counter type by using TYPE_COUNTER and TYPE_SECTORS
in BCH_PERSISTENT_COUNTERS().

Fixes: 1c6fdbd8f246 ("bcachefs: Initial commit")
Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>