Add feature flag for loading app image startup cache

Passed from the zygote.

If false, app image string intern tables and preresolved strings are not
loaded. This means the intern strings are generated by walking the image
instead of looking at the app image intern table directly.

Bug: 123524494
Bug: 116059983
Test: test-art-host
Test: adb shell device_config put runtime_native use_app_image_startup_cache true

Change-Id: I119948efd25c039a057f283c19b23431093659f4