Add a version of SettingsObserver to BinderCallsStats and make it public so it could be

used to collect binder latency data from bluetooth and telephony.

This is a direct cherry pick from internal with no changes: https://googleplex-android-review.git.corp.google.com/c/platform/frameworks/base/+/14236409

Test: latency collection is unit tested, this is just an alternative settings configuration
Bug: 180584913
Change-Id: Ide51afb7eb26a96c7692bceb0a22585a74f08aa7
Merged-In: Ide51afb7eb26a96c7692bceb0a22585a74f08aa7