Build hidden API DEX signatures with Soong

Internal master tree is still invoking Doclava with a Makefile build
rule for hidden API, while the remaining Doclava rules have been
migrated to Soong. Do the same for hidden API.

Test: make out/soong/.intermediates/frameworks/base/hiddenapi-lists/android_common/private-dex.txt
Change-Id: Ifa912f8751025b7de24a982a1a227a9c27d18267