tests/thread: Add test for concurrent interning of strings.
tests/thread: Add test for concurrent interning of strings.

Qstr code accesses global state and needs to be made thread safe.

HenrikSolver/micropython,TDAbboud/micropython,dxxb/micropython,alex-robbins/micropython,ganshun666/micropython,adafruit/circuitpython,SHA2017-badge/micropython-esp32,toolmacher/micropython,toolmacher/micropython,adafruit/circuitpython,lowRISC/micropython,MrSurly/micropython-esp32,oopy/micropython,swegener/micropython,alex-march/micropython,alex-robbins/micropython,bvernoux/micropython,kerneltask/micropython,tuc-osg/micropython,TDAbboud/micropython,deshipu/micropython,Peetz0r/micropython-esp32,cwyark/micropython,PappaPeppar/micropython,henriknelson/micropython,Peetz0r/micropython-esp32,Timmenem/micropython,turbinenreiter/micropython,ryannathans/micropython,cwyark/micropython,pramasoul/micropython,matthewelse/micropython,PappaPeppar/micropython,HenrikSolver/micropython,alex-march/micropython,oopy/micropython,chrisdearman/micropython,HenrikSolver/micropython,adafruit/circuitpython,alex-march/micropython,torwag/micropython,micropython/micropython-esp32,deshipu/micropython,hiway/micropython,jmarcelino/pycom-micropython,trezor/micropython,jmarcelino/pycom-micropython,selste/micropython,pramasoul/micropython,infinnovation/micropython,tobbad/micropython,turbinenreiter/micropython,Timmenem/micropython,blazewicz/micropython,infinnovation/micropython,MrSurly/micropython,blazewicz/micropython,MrSurly/micropython-esp32,trezor/micropython,ryannathans/micropython,ryannathans/micropython,pfalcon/micropython,PappaPeppar/micropython,puuu/micropython,tobbad/micropython,pfalcon/micropython,redbear/micropython,HenrikSolver/micropython,PappaPeppar/micropython,alex-march/micropython,hiway/micropython,blazewicz/micropython,AriZuu/micropython,henriknelson/micropython,swegener/micropython,PappaPeppar/micropython,toolmacher/micropython,mhoffma/micropython,ganshun666/micropython,trezor/micropython,alex-robbins/micropython,hosaka/micropython,dmazzella/micropython,matthewelse/micropython,trezor/micropython,toolmacher/micropython,oopy/micropython,ryannathans/micropython,pozetroninc/micropython,dmazzella/micropython,matthewelse/micropython,AriZuu/micropython,TDAbboud/micropython,Timmenem/micropython,puuu/micropython,mhoffma/micropython,emfcamp/micropython,dxxb/micropython,infinnovation/micropython,MrSurly/micropython,ganshun666/micropython,ryannathans/micropython,micropython/micropython-esp32,mhoffma/micropython,AriZuu/micropython,tuc-osg/micropython,torwag/micropython,alex-robbins/micropython,tuc-osg/micropython,pramasoul/micropython,hiway/micropython,tralamazza/micropython,tuc-osg/micropython,dmazzella/micropython,oopy/micropython,deshipu/micropython,hiway/micropython,bvernoux/micropython,puuu/micropython,SHA2017-badge/micropython-esp32,lowRISC/micropython,dxxb/micropython,jmarcelino/pycom-micropython,emfcamp/micropython,tobbad/micropython,adafruit/micropython,SHA2017-badge/micropython-esp32,alex-march/micropython,deshipu/micropython,pozetroninc/micropython,lowRISC/micropython,adafruit/circuitpython,pramasoul/micropython,TDAbboud/micropython,oopy/micropython,swegener/micropython,torwag/micropython,tralamazza/micropython,emfcamp/micropython,pfalcon/micropython,hosaka/micropython,kerneltask/micropython,pozetroninc/micropython,henriknelson/micropython,blazewicz/micropython,bvernoux/micropython,pfalcon/micropython,infinnovation/micropython,pozetroninc/micropython,adafruit/micropython,turbinenreiter/micropython,puuu/micropython,matthewelse/micropython,chrisdearman/micropython,trezor/micropython,bvernoux/micropython,ganshun666/micropython,dxxb/micropython,lowRISC/micropython,hiway/micropython,henriknelson/micropython,infinnovation/micropython,chrisdearman/micropython,TDAbboud/micropython,puuu/micropython,cwyark/micropython,adafruit/circuitpython,Timmenem/micropython,tralamazza/micropython,tralamazza/micropython,SHA2017-badge/micropython-esp32,tuc-osg/micropython,emfcamp/micropython,tobbad/micropython,AriZuu/micropython,hosaka/micropython,MrSurly/micropython-esp32,Peetz0r/micropython-esp32,HenrikSolver/micropython,selste/micropython,AriZuu/micropython,Timmenem/micropython,kerneltask/micropython,redbear/micropython,cwyark/micropython,swegener/micropython,pfalcon/micropython,jmarcelino/pycom-micropython,micropython/micropython-esp32,MrSurly/micropython-esp32,matthewelse/micropython,lowRISC/micropython,hosaka/micropython,alex-robbins/micropython,ganshun666/micropython,tobbad/micropython,dxxb/micropython,micropython/micropython-esp32,torwag/micropython,hosaka/micropython,chrisdearman/micropython,SHA2017-badge/micropython-esp32,redbear/micropython,kerneltask/micropython,jmarcelino/pycom-micropython,selste/micropython,kerneltask/micropython,MrSurly/micropython,adafruit/micropython,swegener/micropython,henriknelson/micropython,turbinenreiter/micropython,redbear/micropython,adafruit/micropython,redbear/micropython,blazewicz/micropython,mhoffma/micropython,Peetz0r/micropython-esp32,bvernoux/micropython,selste/micropython,toolmacher/micropython,adafruit/circuitpython,chrisdearman/micropython,deshipu/micropython,dmazzella/micropython,micropython/micropython-esp32,MrSurly/micropython,pramasoul/micropython,emfcamp/micropython,MrSurly/micropython,torwag/micropython,cwyark/micropython,pozetroninc/micropython,matthewelse/micropython,turbinenreiter/micropython,Peetz0r/micropython-esp32,MrSurly/micropython-esp32,selste/micropython,mhoffma/micropython,adafruit/micropython