add utilities for deleting on-disk leveldb data
Used in later commits to remove leveldb directories for
- invalid snapshot chainstates, and
- background-vaildation chainstates that have finished serving their purpose.
https://github.com/bitcoin/bitcoin/pull/25667/commits/34d159033106cc595cfa852695610bfe419c989c
validation: remove snapshot datadirs upon validation failure
If a UTXO snapshot fails to validate, don't leave the resulting datadir
on disk as this will confuse initialization on next startup and we'll
get an assertion error.
https://github.com/bitcoin/bitcoin/pull/25667/commits/ad67ff377c2b271cb4683da2fb25fd295557f731
This is a partial backport of core#25667
Depends on D14653