android build: Split process_resources GN rule and script.

This is a reland of [1] which got reverted in [2] because the
former actual broke the internal official build of Clank.

It turns out that instead of removing |app_as_shared_library = true|,
for the monochrome apk template, it should be turned into
|shared_resources = true|.

Apart from that, see description of the change in the original
CL, everything still applies.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/957095
[2] https://chromium-review.googlesource.com/c/chromium/src/+/968461

R=agrieve@chromium.org,yfriedman@chromium.org,estevenson@chromium.org,trevordixon@chromium.org

Bug: 820459
Change-Id: I6f6e71c3a13a388c67b68b684c733cd549a2cef0
Reviewed-on: https://chromium-review.googlesource.com/968870
Reviewed-by: agrieve <agrieve@chromium.org>
Commit-Queue: David Turner <digit@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544300}
7 files changed