HH-42371 fix AsyncGroup implementation
HH-42371 fix docs and speed up unittests, fix PEP8
HH-43401 set ensure_ascii=False in JsonProducer
HH-43401 escape apos in copy as curl
Merge remote-tracking branch 'origin/HH-43401' into EXP-11315
Merge remote-tracking branch 'origin/HH-42371' into EXP-11315
release 2.19.15 [an.sumin@hh.ru]