os::trace_page_sizes_for_requested_size should name alignment as requested page size

os::trace_page_sizes_for_requested_size() names "alignment" what is actually the requested page size.

I propose to rename "alignment" to "requested page size" in os::trace_page_sizes_for_requested_size() since it clearer conveys the difference between requested and actual page size, which is the important bit for pagesize logging.