Add HIDDEN_API_POLICY to @TestApi.i

This is a cherry-pick from internal master.

Test: cd cts/tests/signature; atest
Bug: 170428909
Bug: 169987505
Merged-In: I68231850a000243cd01ba066585322cab7608884
Change-Id: I68231850a000243cd01ba066585322cab7608884
3 files changed