Move hiddenapi singleton rules to Soong

Hiddenapi rules are now in build/soong/java/hiddenapi_singleton.go.
This effectively requires any module in PRODUCT_BOOT_JARS to be
defined in Soong.

Bug: 123645297
Test: m checkbuild
Change-Id: If72bd1c20b2014d0a3d400624d37fdb0a3052245