Add a check for apex/allowed_deps.txt to droidcore.

The check ensures that build graph for updatable modules contains only
allowed dependencies at build time.

Bug: 149622332
Test: m
Change-Id: I52a4be72efaa523d53827dd11822a7802543dd10
(cherry picked from commit c72ee9cd023b76db6a365e0ff2e46fa791e64cc2)