Previously, the `utxocache:flush` tracepoint was in the wrong scope and
reached every time `CChainState::FlushStateToDisk` was called, even when
there was no flushing of the cache. The tracepoint is now properly scoped
and will be reached during a full flush.
This concludes backport of [[https://github.com/bitcoin/bitcoin/pull/23907 | core#23907]]
https://github.com/bitcoin/bitcoin/pull/23907/commits/36a65847033540cf2203252c7baf42bc5ec97579