Add support for sharding tests. (#2537) #2982

Job	Run time
Check GitHub Organization	1s
tox -e format-check,lint-check,typecheck,vendor-check,package,docs	8m 37s
./dtox.sh -e py27-pip20	8m 18s
tox -e py312-pip24_2	10m 25s
./dtox.sh -e py37-pip20	10m 47s
tox -e py312-pip24_2-integration	1h 9m 56s
./dtox.sh -e py311-pip20	10m 30s
./dtox.sh -e py311-pip22_3_1	11m 16s
./dtox.sh -e py311-pip23_1_2	10m 52s
./dtox.sh -e py312-pip24_2	10m 53s
./dtox.sh -e py313-pip24_2	9m 35s
./dtox.sh -e pypy310-pip20	18m 4s
./dtox.sh -e pypy310-pip22_3_1	18m 25s
./dtox.sh -e pypy310-pip23_1_2	16m 59s
./dtox.sh -e py27-pip20-integration	25m 27s
./dtox.sh -e py37-pip22_3_1-integration	54m 59s
./dtox.sh -e py37-pip23_1_2-integration	55m 42s
./dtox.sh -e py311-pip20-integration	35m 3s
./dtox.sh -e py311-pip22_3_1-integration	42m 17s
./dtox.sh -e py311-pip23_1_2-integration	40m 2s
./dtox.sh -e py312-pip24_2-integration	47m 4s
./dtox.sh -e py313-pip24_2-integration	40m 9s
./dtox.sh -e pypy310-pip20-integration	1h 2m 34s
./dtox.sh -e pypy310-pip22_3_1-integration	1h 13m 20s
./dtox.sh -e pypy310-pip23_1_2-integration	1h 8m 19s
Gather Final Status	1s
	12h 39m 35s

Provide feedback