Merge changes I7940d56b,Iaec6ffe7,I0a6d3219,Idfd77557,Ia14d3260, ... into main

* changes:
  [7/N] Simplify Service/Provider policy method signatures
  [6/N] Delete OomAdjusterLegacyImpl and rename the Modern impl
  [5/N] Remove the ability to select the Legacy OomAdjuster impl
  [4/N] Remove unused code paths in each OomAdjuster impl
  [3/N] Copy OomAdjuster compute methods to individual impls
  [2/N] Move Legacy only methods calls to OomAdjusterLegacyImpl
  [1/N] Turn OomAdjuster into an abstract base class