aconfig: add new codegen mode force_read_only am: 1a8281cc am: fc11f98b am: 7cffcf40

Original change: https://android-review.googlesource.com/c/platform/build/+/2887246



Change-Id: I9b2f3a19d3d0a1b8c962aeb68c48aa7417515e82
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>