Investigate simplifying printing of thread bindings

[msimberg]

--pika:print-bind is currently handled at a very late stage, inside the run_helper task before pika_main is run. This is presumably done so that it happens after "late" command line options have been handled. However, it's not clear that we still need the late command line handling. If we don't need it, we could possibly simplify handling of --pika:print-bind by handling it after the resource partitioner has been created and before run_helper is created. One issue that may prevent us from simplifying this is the consistency check between pika and hwloc process bindings which is also done while handling --pika:print-bind. However, that check could possibly be moved to a new place if we decide to keep it.