Add tab-completion support to PEX repls. #2413

Job	Run time
Check GitHub Organization	1s
tox -e format-check,lint-check,typecheck,vendor-check,package	4m 44s
tox -e py312-pip23_3_2-integration	3m 23s
./dtox.sh -e py27-pip20-integration	3m 36s
./dtox.sh -e py37-pip22_3_1-integration	2m 49s
./dtox.sh -e py37-pip23_1_2-integration	3m 35s
./dtox.sh -e py311-pip20-integration	2m 55s
./dtox.sh -e py311-pip22_3_1-integration	3m 33s
./dtox.sh -e py311-pip23_1_2-integration	3m 29s
./dtox.sh -e py312-pip23_3_2-integration	3m 35s
./dtox.sh -e py313-pip24_0-integration	3m 22s
./dtox.sh -e pypy310-pip20-integration	3m 55s
./dtox.sh -e pypy310-pip22_3_1-integration	3m 12s
./dtox.sh -e pypy310-pip23_1_2-integration	4m 23s
Gather Final Status	0s
	46m 32s

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