bcachefs: enum bch_persistent_counters_stable

bcachefs: enum bch_persistent_counters_stable

Persistent counters, like recovery passes, include a stable enum in
their definition - but this was never correctly plumbed.

This allows us to add new counters and properly organize them with a
non-stable "presentation order", which can also be used in userspace by
the new 'bcachefs fs top' tool.

Fortunatel, since we haven't yet added any new counters where
presentation order ID doesn't match stable ID, this won't cause any
reordering issues.

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