DefaultWorkerTool: create a single `Tool` object
DefaultWorkerTool: create a single `Tool` object

Summary:
This eagerly creates and stores the inner `Tool` object, rather than new'ing
one up on each call to `getTool()`.  Since this `Tool` is a `RuleKeyAppendable`,
we rely on instance equality to get hits in the rule key cache.

Test Plan: CI

fbshipit-source-id: 633daf6

robbertvanginkel/buck,ilya-klyuchnikov/buck,shs96c/buck,facebook/buck,zhan-xiong/buck,facebook/buck,SeleniumHQ/buck,robbertvanginkel/buck,kageiit/buck,davido/buck,ilya-klyuchnikov/buck,dsyang/buck,shybovycha/buck,darkforestzero/buck,JoelMarcey/buck,robbertvanginkel/buck,k21/buck,kageiit/buck,k21/buck,zpao/buck,darkforestzero/buck,vschs007/buck,Addepar/buck,k21/buck,LegNeato/buck,grumpyjames/buck,romanoid/buck,ilya-klyuchnikov/buck,brettwooldridge/buck,darkforestzero/buck,romanoid/buck,shs96c/buck,rmaz/buck,shybovycha/buck,SeleniumHQ/buck,Addepar/buck,marcinkwiatkowski/buck,darkforestzero/buck,JoelMarcey/buck,grumpyjames/buck,grumpyjames/buck,dsyang/buck,brettwooldridge/buck,k21/buck,clonetwin26/buck,grumpyjames/buck,dsyang/buck,marcinkwiatkowski/buck,vschs007/buck,JoelMarcey/buck,davido/buck,SeleniumHQ/buck,k21/buck,k21/buck,ilya-klyuchnikov/buck,clonetwin26/buck,LegNeato/buck,davido/buck,robbertvanginkel/buck,ilya-klyuchnikov/buck,davido/buck,dsyang/buck,facebook/buck,ilya-klyuchnikov/buck,Addepar/buck,brettwooldridge/buck,clonetwin26/buck,kageiit/buck,shybovycha/buck,nguyentruongtho/buck,darkforestzero/buck,shybovycha/buck,davido/buck,LegNeato/buck,LegNeato/buck,davido/buck,grumpyjames/buck,robbertvanginkel/buck,darkforestzero/buck,LegNeato/buck,vschs007/buck,romanoid/buck,vschs007/buck,grumpyjames/buck,rmaz/buck,ilya-klyuchnikov/buck,rmaz/buck,nguyentruongtho/buck,robbertvanginkel/buck,LegNeato/buck,darkforestzero/buck,darkforestzero/buck,darkforestzero/buck,grumpyjames/buck,marcinkwiatkowski/buck,brettwooldridge/buck,robbertvanginkel/buck,shs96c/buck,zpao/buck,shs96c/buck,LegNeato/buck,k21/buck,darkforestzero/buck,zhan-xiong/buck,davido/buck,marcinkwiatkowski/buck,grumpyjames/buck,marcinkwiatkowski/buck,romanoid/buck,romanoid/buck,zpao/buck,rmaz/buck,marcinkwiatkowski/buck,grumpyjames/buck,ilya-klyuchnikov/buck,zhan-xiong/buck,LegNeato/buck,JoelMarcey/buck,shybovycha/buck,dsyang/buck,zhan-xiong/buck,zhan-xiong/buck,romanoid/buck,dsyang/buck,brettwooldridge/buck,dsyang/buck,facebook/buck,romanoid/buck,facebook/buck,marcinkwiatkowski/buck,shybovycha/buck,JoelMarcey/buck,marcinkwiatkowski/buck,k21/buck,zpao/buck,marcinkwiatkowski/buck,dsyang/buck,clonetwin26/buck,ilya-klyuchnikov/buck,JoelMarcey/buck,brettwooldridge/buck,nguyentruongtho/buck,davido/buck,darkforestzero/buck,facebook/buck,SeleniumHQ/buck,Addepar/buck,Addepar/buck,vschs007/buck,clonetwin26/buck,LegNeato/buck,zhan-xiong/buck,shs96c/buck,grumpyjames/buck,clonetwin26/buck,JoelMarcey/buck,LegNeato/buck,vschs007/buck,grumpyjames/buck,k21/buck,vschs007/buck,dsyang/buck,robbertvanginkel/buck,rmaz/buck,clonetwin26/buck,zhan-xiong/buck,vschs007/buck,SeleniumHQ/buck,robbertvanginkel/buck,shs96c/buck,darkforestzero/buck,dsyang/buck,shs96c/buck,SeleniumHQ/buck,dsyang/buck,shybovycha/buck,JoelMarcey/buck,zhan-xiong/buck,shs96c/buck,davido/buck,shs96c/buck,brettwooldridge/buck,JoelMarcey/buck,rmaz/buck,clonetwin26/buck,kageiit/buck,robbertvanginkel/buck,Addepar/buck,shybovycha/buck,clonetwin26/buck,nguyentruongtho/buck,davido/buck,k21/buck,shs96c/buck,SeleniumHQ/buck,Addepar/buck,davido/buck,SeleniumHQ/buck,kageiit/buck,robbertvanginkel/buck,JoelMarcey/buck,zpao/buck,Addepar/buck,zhan-xiong/buck,brettwooldridge/buck,SeleniumHQ/buck,rmaz/buck,LegNeato/buck,shybovycha/buck,vschs007/buck,rmaz/buck,zhan-xiong/buck,nguyentruongtho/buck,dsyang/buck,clonetwin26/buck,zhan-xiong/buck,brettwooldridge/buck,kageiit/buck,brettwooldridge/buck,nguyentruongtho/buck,Addepar/buck,shybovycha/buck,davido/buck,ilya-klyuchnikov/buck,vschs007/buck,clonetwin26/buck,LegNeato/buck,facebook/buck,romanoid/buck,zhan-xiong/buck,k21/buck,JoelMarcey/buck,shybovycha/buck,Addepar/buck,ilya-klyuchnikov/buck,Addepar/buck,SeleniumHQ/buck,romanoid/buck,rmaz/buck,vschs007/buck,shybovycha/buck,vschs007/buck,k21/buck,kageiit/buck,shs96c/buck,nguyentruongtho/buck,robbertvanginkel/buck,SeleniumHQ/buck,ilya-klyuchnikov/buck,darkforestzero/buck,romanoid/buck,Addepar/buck,marcinkwiatkowski/buck,vschs007/buck,clonetwin26/buck,dsyang/buck,rmaz/buck,zhan-xiong/buck,rmaz/buck,JoelMarcey/buck,k21/buck,brettwooldridge/buck,davido/buck,shs96c/buck,romanoid/buck,romanoid/buck,robbertvanginkel/buck,rmaz/buck,brettwooldridge/buck,zpao/buck,marcinkwiatkowski/buck,clonetwin26/buck,JoelMarcey/buck,LegNeato/buck,Addepar/buck,SeleniumHQ/buck,shs96c/buck,rmaz/buck,marcinkwiatkowski/buck,ilya-klyuchnikov/buck,grumpyjames/buck,marcinkwiatkowski/buck,romanoid/buck,zpao/buck,SeleniumHQ/buck,shybovycha/buck,brettwooldridge/buck