Compare undefined fields of Configuration in ResourcesKey

By default diffPublicOnly doesn't compare undefined, that will
cause an empty config to match any other non empty config.

Also correct the object to compare.

Bug: 413273054
Flag: android.content.res.ignore_non_public_config_diff_for_resources_key
Test: atest FrameworksCoreTests:ResourcesManagerTest# \
      testNonPublicDiffOverrideConfigShareImpl
Change-Id: I23cc94da673326343f30fbb0e4865d500c4afec2