format: remove all implicit ref handling outside of libfmt_macros

format: remove all implicit ref handling outside of libfmt_macros

format: beautifully get rid of ArgumentNext and CountIsNextParam

Now that CountIsNextParam and ArgumentNext are resolved during parse,
the need for handling them outside of libfmt_macros is obviated.

Note: *one* instance of implicit reference handling still remains, and
that's for implementing `all_args_simple`. It's trivial enough though,
so in this case it may be tolerable.