refactor(@angular/build): optimize vitest in-memory file loading #9269

Job	Run time
build	13s
lint	12s
build-e2e-windows	13s
Browser Compatibility Tests	1s
e2e-windows	1s
publish-snapshots	1s
e2e	1s
e2e-snapshots	1s
test	1s
e2e-package-managers	1s
	45s

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