This reverts aeb089ecc7, which introduced
logging, adding a dependency on libbitcoin_util.a to libzcashconsensus.a.
Also adds missing #includes that were being indirectly included via
prevector.h including util.h.
Based on bitcoin/bitcoin#13021 but implemented from scratch.
This introduces a cyclic dependency between `logging` and `util` that
should be cleaned up in a future PR.