[clang-tidy] Allow disabling support for NOLINTBEGIN/NOLINTEND blocks.

This patch parameterizes the clang-tidy diagnostic consumer with a boolean that
controls whether to honor NOLINTBEGIN/NOLINTEND blocks. The current support for
scanning these blocks is very costly -- O(n*m) in the size of files (n) and
number of diagnostics found (m), with a large constant factor.  So, the patch
allows clients to disable it.

Future patches should make the feature more efficient, but this will mitigate in
the interim.

Differential Revision: https://reviews.llvm.org/D114981