[backport#18417 1/3] tests: Add fuzzing harness for functions in addrdb.h

Summary:
https://github.com/bitcoin/bitcoin/pull/18417/commits/a8695db7851dabdda08b2ec9a68d6a27c0e2fdc4

Depends on D7132

Partial backport of Core PR18417

Test Plan:

cmake -GNinja .. -DENABLE_SANITIZERS="address;fuzzer" -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++
ninja bitcoin-fuzzers
./src/test/fuzz/addrdb

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D7133