Merge "Add ability to say a custom partition doesn't want to participate in...

Merge "Add ability to say a custom partition doesn't want to participate in fastboot flashall" into main am: d8ac6c96

Original change: https://android-review.googlesource.com/c/platform/build/+/3518233



Change-Id: I7848986eff83770a80b98b01c6a796e11272c99e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>