[QA] Allow addrman loopback tests (add debug option -addrmantest)

Summary:
This add a new debug option which will be later used to test network
limited nodes.

Partial backport of core PR10387 (commit fa999af)

Test Plan:

make check

../configure --enable-debug && make
./src/bitcoind --help -help-debug

Check the -addrmantest argument documentation is correct

./src/bitcoind -regtest -datadir=<some_non_default_data_dir> &
./src/bitcoind -regtest -debug=all -addnode=127.0.0.1 -addrmantest=1 &
grep AdvertiseLocal ~/.bitcoin/regtest/debug.log

Check the grep outputs something containing:

AdvertiseLocal: advertising address 127.0.0.1

Reviewers: #bitcoin_abc, deadalnix, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2388