This commit:
* moves bandwidth checks into dirauth_config, and
* moves some other minor checks into dirauth_config.
The moved code is disabled when the dirauth module is disabled.
(And some of the checks are re-ordered, so the order of some
warnings may change.)
Part of 32213.
This commit:
* creates feature/dirauth/dirauth_config.[ch],
* moves the dirauth config code into them,
* copies some macros from src/app/config.c
(we'll refactor them later in 29211), and
* adds thin wrappers to make the moved code compile.
No functional changes: the moved code is still enabled,
even if the dirauth module is disabled.
Part of 32213.
