fix(@schematics/angular): add warnings and improve Karma config gener… #9071

Job	Run time
lint	2m 26s
build	2m 46s
build-e2e-windows	2m 46s
e2e-windows	1s
test	1s
publish-snapshots	1s
Browser Compatibility Tests	1s
e2e-snapshots	1s
e2e-package-managers	1s
e2e	1s
	8m 5s

Provide feedback