tests: Fill fuzzing coverage gaps for functions in primitives/block.h

Summary:

Fill fuzzing coverage gaps for functions in consensus/validation.h
Fill fuzzing coverage gaps for functions in primitives/block.h
Fill fuzzing coverage gaps for functions in util/translation.h
[...]

Backport of core PR18938.

The last commit is almost empty as we already enforce c++17 and run
clang-format for each diff. Only remains the standard library additions
in src/fuzz/test/script.cpp.

Test Plan:

ninja bitcoin-fuzzers
./test/fuzz/test_runner.py <path_to_corpus>

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D9061