Read Java constant pool to generate keep rules for async VR DFM

Add bytecode rewriter method to read super classes, implemented
interfaces, and field and method references from class constant pools.
Convert list of references to keep rules.
Integrate new keep rules into build to ensure VR stays compatible with
base when proguarded separately.

Bug: 952838
Change-Id: I0c9c44b1aa02cc9862ae3b03110e947fb28b6a3b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1560013
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Commit-Queue: Anthony Cui <cuianthony@google.com>
Cr-Commit-Position: refs/heads/master@{#654028}
10 files changed