fix(@angular/build): add filename truncation to test discovery #2435

Job	Run time
lint	1m 50s
build-e2e-windows	26s
build	32s
e2e-windows	0s
Browser Compatibility Tests	0s
test	0s
publish-snapshots	0s
e2e	0s
e2e-snapshots	0s
e2e-package-managers	0s
	2m 48s

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