libbinder_random_parcel: fuzz mult binders

We fuzz multiple binders and those that they return
internally. Now, we expose an API that allows you to
fuzz a group of services at the same time.

Test: servicemanager_fuzzer for a few minutes (CPP backend)
Test: android.hardware.vibrator-service.example_fuzzer for a few minutes (NDK backend)
Fixes: 282961568
Change-Id: I4f511243e0a743f67d52c7b3287c751cb96e0e50