feat: set names to threads

[jesterhodl]

Fixes #148

BEFORE:
ps -T -p 2987412 -o pid,tid,comm,args
    PID     TID COMMAND         COMMAND
2987412 2987412 datum_gateway   ./datum_gateway
2987412 2987413 datum_gateway   ./datum_gateway
2987412 2987414 datum_gateway   ./datum_gateway
2987412 2987415 datum_gateway   ./datum_gateway
2987412 2987416 datum_gateway   ./datum_gateway
2987412 2987417 datum_gateway   ./datum_gateway
2987412 2987418 MHD-single      ./datum_gateway
2987412 2987419 datum_gateway   ./datum_gateway
2987412 2987420 datum_gateway   ./datum_gateway
2987412 2987421 datum_gateway   ./datum_gateway

AFTER:
ps -T -p 2993005 -o pid,tid,comm,args
    PID     TID COMMAND         COMMAND
2993005 2993005 datum_gateway   ./datum_gateway
2993005 2993006 logger          ./datum_gateway
2993005 2993007 api             ./datum_gateway
2993005 2993008 coinbaser       ./datum_gateway
2993005 2993009 template        ./datum_gateway
2993005 2993010 stratum         ./datum_gateway
2993005 2993011 MHD-single      ./datum_gateway
2993005 2993012 fallback        ./datum_gateway
2993005 2993013 submitblock     ./datum_gateway
2993005 2993014 listener        ./datum_gateway

[luke-jr]

Slight preference for simply defining pthread_setname_np no-op when it's missing (and calling directly in the code)

[jesterhodl]

force-pushed a clean version taking this into account