metrics: fix compaction pending bytes metrics in fast tune (#8994)
metrics: fix compaction pending bytes metrics in fast tune (#8994)

Signed-off-by: Xinye Tao <9573dceb6ead9846c7438fed8e7eb148b78d187d@outlook.com>
BusyJay/tikv,pingcap/tikv,pingcap/tikv,BusyJay/tikv,BusyJay/tikv,BusyJay/tikv,c4pt0r/tikv