API tweaks.

Minor tweaks to the API surface implementation:

* Ensure collections are immutable rather than making copies in getters
* Fix one parcelable impl that wasn't using TypedObject API
* Minor fixes to documentations
* Apply minor suggestions from IntelliJ
* Format / move around code in a consistent way

Bug: 224511628
Bug: 224510831
Bug: 224513048
Test: atest CtsSafetyCenterTestCases

Change-Id: I78bd690e0272605d0205c2c64a1bfb4ce800122e