[7/N] Simplify Service/Provider policy method signatures

Now that the Legacy OomAdjuster is gone, many of the arguments are no
longer needed.

Flag: EXEMPT pure refactor
Test: atest MockingOomAdjusterTests
Test: builds and flashes
Bug: 306731120
Change-Id: I7940d56bed08a6857b9e953697ed5594b8b47f8d