Android: Remove from manifest: android:appComponentFactory

It's a feature that we don't use, and causes scary stack to be printed
when incremental_install=true

Also made some comments from BuildConfigGenerator.groovy be written out
to BUILD.gn (but didn't actually run fetch_all.py due to androidx
transition).

Bug: 1025357
Change-Id: Iac87d758b330c130a1bcd96ec91922020594ccce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2122234
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Peter Wen <wnwen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#753738}