Clarify when IGnss.hal cleanup() and setCallback() methods are called

Update IGnss.hal cleanup() and setCallback() method documentation to
clarify when the framework calls these methods so that the GNSS engine
knows when to shut down for power savings.

This CL updates @1.1::IGnss.hal and @1.0::IGnss.hal interfaces only.
@2.0::IGnss.hal is updated in another CL.

Bug: 124104175
Test: Existing tests pass
Change-Id: I8181251677dab78ce0619fa1e2a667b36e115f25