Fix hidden API flags decoding for intrinsics

Hidden API decision logic would try to decode the access flags of
intrinsics directly, bypassing the override in ArtMethod. This patch
get hidden_api.h to use the same code path.

This also fixes CtsHiddenApiDiscoveryTestCases where the access flags
of blacklisted APIs are tested. VarHandle intrinsics would not pass.

Bug: 64382372
Bug: 72430785
Bug: 78230396
Test: cts-tradefed run cts --module CtsHiddenApiDiscoveryTestCases
Change-Id: I080313dd91bbee2d7d98b00c02e224974b344c01