Provide error handling for nullptr in the ADPF NDK

Currently there is very little error handling for null pointers
in the NDK, so this CL aims to remedy that by changing the WorkDuration
API to pass status messages, updating the relevant documentation,
and making sure that all existing methods check all pointers
that are passed.

Bug: 321065424
Test: atest PerformanceHintNativeTestCases
Test: atest PerformanceHintManagerTest
Test: atest HintManagerServiceTest
Change-Id: I8be8bb7a24e861855176c52231c48479e603aa42