[AsmPrinter] fix -disable-debug-info option

This option was in a rather convoluted place, causing global parameters
to be set in awkward and undesirable ways to try to account for it
indirectly. Add tests for the -disable-debug-info option and ensure we
don't print unintended markers from unintended places.

Reviewed By: dstenb

Differential Revision: https://reviews.llvm.org/D91083