Switch vendoring from RedBaron to libcst. (#2654) #3347

Job	Run time
Check GitHub Organization	1s
tox -e py313-pip25_0	19m 50s
./dtox.sh -e py27-pip20	9m 21s
tox -e py313-pip25_0-integration --shard 1/2	36m 5s
tox -e format-check,lint-check,typecheck,enum-check,vendor-check,package,docs	8m 28s
./dtox.sh -e py38-pip22_3_1	18m 11s
tox -e py313-pip25_0-integration --shard 2/2	29m 58s
./dtox.sh -e py311-pip23_3_2	18m 11s
./dtox.sh -e py313-pip25_0	14m 45s
./dtox.sh -e py314-pip25_0	14m 22s
./dtox.sh -e pypy310-pip24_3_1	29m 50s
./dtox.sh -e py27-pip20-integration	29m 56s
./dtox.sh -e py38-pip22_3_1-integration --shard 1/2	28m 53s
./dtox.sh -e py38-pip22_3_1-integration --shard 2/2	27m 19s
./dtox.sh -e py311-pip23_3_2-integration --shard 1/2	28m 31s
./dtox.sh -e py311-pip23_3_2-integration --shard 2/2	25m 49s
./dtox.sh -e py313-pip25_0-integration --shard 1/2	25m 49s
./dtox.sh -e py313-pip25_0-integration --shard 2/2	24m 45s
./dtox.sh -e py314-pip25_0-integration --shard 1/2	26m 5s
./dtox.sh -e py314-pip25_0-integration --shard 2/2	25m 55s
./dtox.sh -e pypy310-pip24_3_1-integration --shard 1/2	52m 48s
./dtox.sh -e pypy310-pip24_3_1-integration --shard 2/2	51m 5s
Gather Final Status	1s
	9h 5m 58s

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