abitidy: Add method to calculate new ids for anonymous types am: 4ccad53441 am: 1aed691eab

Original change: https://android-review.googlesource.com/c/platform/external/libabigail/+/2197899

Change-Id: I0b936b28c85b9ce1aa83caa9e116b52d21c45e3e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>