[modules] Verify module signature when faking on-demand install

To make this work this CL adds a specific build of the Play Core SDK
that exposes a verification method.

Bug: 901920
Change-Id: Icbf15a17f9345085d8ccd812d50d208f5279fe49
Reviewed-on: https://chromium-review.googlesource.com/c/1338563
Reviewed-by: Scott Violet <[email protected]>
Reviewed-by: agrieve <[email protected]>
Commit-Queue: Tibor Goldschwendt <[email protected]>
Cr-Commit-Position: refs/heads/master@{#608991}
14 files changed