Complete missing argument documentation

Summary:
Add documentation for the -finalizationdelay and -maxreorgdepth args,
set documentation optional for -parkdeepreorg and -replayprotectionactivationtime.

Depends on D2318

Test Plan:

./contrib/devtools/check-doc.py

Ensure it returns 0 undocumented argument.

./src/bitcoind --help

Check the arguments are correctly documented

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2299