workers,trace_events: set thread name for workers

Set the thread name for workers in trace events. Also,
use uint64_t for thread_id_ because there's really no
reason for those to be doubles

PR-URL: https://github.com/nodejs/node/pull/21246


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>