releasetools: Replace Trichrome fingerprint

* Trichrome APKs depend on TrichromeLibrary, and they
  specify both package name and a certificate digest
* We sign TrichromeLibrary and both dependent APKs
  with the same key, so we can simply
  make sure that the fingerprint matches the key
  the APK is being (re)signed with

Based on: https://github.com/danielfullmer/robotnix/blob/master/modules/apps/chromium-trichrome-patcher.py

Change-Id: I79f8c69787decd5abbb5d5513dee9bc357eb8814