[CMAKE] Add an option to promote some warnings to errors

Summary: This is a cmake port of the autotools --enable-werror option.

Test Plan:

cmake -GNinja -DENABLE_WERROR=ON ..
ninja check

Reviewers: #bitcoin_abc, deadalnix, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D4697