Fix check-doc.py

Summary:
Update the script to work with our codebase, especially our clang-format
rules.

Test Plan:

contrib/devtools/check-doc.py

The expected ouput should contain:

• The number of arguments used through the code (via the getters from ArgsManager)
• The number of arguments documented in the code (via the HelpMessageOpt calls)
• The deduced quantity and list of:
  • Undocumented arguments (arguments used but not documented)
  • Unknown arguments (arguments documented but not used)

The script exit code is the number of undocumented arguments.

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2280