Use ubuntu-latest-16-cores from CNCF for e2e #3799

Job	Run time
e2e (v1.29.8, v0.56.8)	20m 13s
test-docker-build (base)	40s
e2e (v1.29.8, v0.65.5)	21m 14s
test-docker-build (git)	1m 9s
integration (v1.29.8, v0.56.8)	27m 29s
e2e (v1.31.0, v0.56.8)	26m 13s
test-docker-build (image-processing)	51s
unit	3m 39s
integration (v1.29.8, v0.65.5)	28m 54s
e2e (v1.31.0, v0.65.5)	20m 57s
test-docker-build (waiter)	38s
integration (v1.31.0, v0.56.8)	27m 49s
integration (v1.31.0, v0.65.5)	28m 18s
	3h 28m 4s

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