feat(@angular/build): rename `experimentalPlatform` to `platform` in … #3232

Job	Run time
list	26s
workflow (devkit-core-tests)	1m 28s
workflow (build-unit-tests)	2m 41s
workflow (devkit-core-tests-rerun)	1m 39s
workflow (modules-builder-tests)	2m 3s
workflow (build-cli)	1m 55s
	10m 12s

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