Prevent shared conf files from failing with different available options in different binaries

Summary:

Options that are not available (but known in the source code) will
cause an error if they are specified.
Make these options "available" by adding them to the hidden options
category to prevent conf files from failing when shared between binaries
that have different options available.

Backport of core PR13441.

This required to re-add exceptions to the check-doc linter, but most
of them are going to be removed by a following diff (PR14272).

Test Plan:

ninja check
./test/functional/test_runner.py
./bitcoind -help

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5054