Refactor: libcrmcommon: move PCMK__OUTPUT_ARGS() to output_internal.h

... from crm_internal.h, since it's output-related.

Until now we've been using crm_internal.h for definitions needed by multiple
libraries, but since the long-term goal is to merge most of the libraries into
libcrmcommon, and libcrmcommon already has definitions used by other libraries
anyway, this moves another step toward crm_internal.h just being a collection
of other includes.