Generate combined deps-info for all updatable modules.

Introduce a singleton apex rule to merge contents of individual
deps-info results into a single output file.

Bug: 149622332
Test: m
Change-Id: I4ab7e1a3527fead97a81a5a2cb0e1e93a429117c
Merged-In: I4ab7e1a3527fead97a81a5a2cb0e1e93a429117c
Exempt-From-Owner-Approval: cp from aosp
(cherry picked from commit 849f8442)