tests: Add fuzzing harness for classes/functions in blockfilter.h. Add integer {de,}serialization fuzzing.

Summary:

Add fuzzing harness for classes/functions in blockfilter.h.

Add integer serialization/deserialization fuzzing harness.

Backport of core PR18423.

Depends on D8967.

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/D8970