Reenable core platform API violation warnings, dedupe

Print a warning the first time a non-core platform API member is
accessed and add kAccCorePlatformApi to its access flags to not report
it next time. Only do this when policy is kJustWarn. This prevents
logspam.

Bug: 125701194
Bug: 119068555
Test: compiles, boots
Test: art/test.py -b -r -t 674
Change-Id: Ia7d6ba4f1f30fbea7bdea1670183c17f84ca1150