Replace base string utils with android::base ones am: 0c18424d12 am: ee687f3903

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/3320834

Change-Id: I7b64920dac17d7cfbf6e8a3d1989431253a985cb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>