Refactor: scheduler: Add a new node-attribute-list message.

This is a larger patch because it involves moving a lot of code from
crm_mon into pe_output.c. I also inlined the print_node_attribute
function, converted a use of g_list_foreach into a manually constructed
loop, and got rid of mon_attr_data. This was all done to make this code
less crm_mon specific and to get rid of things that were really only
being used in one place.

See: rhbz#1686426