Add BinderObserverConfig and default sharding

Add a new BinderObserverConfig class to keep track of the current
sharding config and determine whether stats collection should be
enabled on the process or AIDL level.

Add default sharding parameters and lots of tests.

This is to ensure the overhead of tracking stats is kept at a
reasonable level. Later the sharding parameters will be made
configurable via system properties.

Co-authored by Parth Sane <parthsane@google.com> (see ag/34203654).

Bug: 299356196
Test: atest binderObserverConfigUnitTest
Flag: build.RELEASE_LIBBINDER_BINDER_OBSERVER
Change-Id: I9eebdcb6708ef47d22846c2526a255c9538fb368