perf(@angular/cli): optimize package manager discovery with stat-base… #2684

Job	Run time
build-e2e-windows	21s
build	1m 0s
lint	1m 56s
e2e-windows	0s
test	0s
publish-snapshots	0s
Browser Compatibility Tests	0s
e2e-package-managers	0s
e2e	0s
e2e-snapshots	0s
	3m 17s

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