Convert helper_apps of OverlayHostTests to Android.bp

Bug: 317159909
Test: atest OverlayHostTests
      m OverlayHostTests
      m OverlayHostTests_PlatformSignatureStaticOverlay
      m OverlayHostTests_PlatformSignatureOverlay
      m OverlayHostTests_UpdateOverlaya
      m OverlayHostTests_FrameworkOverlayV1
      m OverlayHostTests_FrameworkOverlayV2
      m OverlayHostTests_AppOverlayV1
      m OverlayHostTests_AppOverlayV2
Change-Id: I14491d2cbaa98ec72de1eb149e1a82a7f061d5d0