Reland "Remove HTTP-Based Public Key Pinning header parsing and persistence code."

This is a reland of e211b725cdb2b5e0e7cb37f45f2126eb09780562,
with fix for NetworkContextTest.CertReporting (restored original behavior of the
test using a testserver to listen for the pkp report).

Original change's description:
> Remove HTTP-Based Public Key Pinning header parsing and persistence code.
>
> And related code that uses it.
>
> Cronet depends on the base dynamic PKP support, so is not removed here.
>
> Based on https://crrev.com/c/1005960 by palmer & nharper.
>
> Bug: 779166
> Cq-Include-Trybots: luci.chromium.try:linux_mojo
> Change-Id: I44044a3960174fcba1f1e120b18cbef3ff769812
> Reviewed-on: https://chromium-review.googlesource.com/c/1260483
> Reviewed-by: Tom Sepez <tsepez@chromium.org>
> Reviewed-by: John Abd-El-Malek <jam@chromium.org>
> Reviewed-by: Ryan Sleevi <rsleevi@chromium.org>
> Reviewed-by: Matt Menke <mmenke@chromium.org>
> Commit-Queue: Ryan Sleevi <rsleevi@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#598657}

TBR=jam@chromium.org

Bug: 779166
Change-Id: I2e3b4dbab9cbbc95606c1cf7051b112fc5ba8cc4
Cq-Include-Trybots: luci.chromium.try:linux_mojo
Reviewed-on: https://chromium-review.googlesource.com/c/1277963
Commit-Queue: Matt Mueller <mattm@chromium.org>
Reviewed-by: Ryan Sleevi <rsleevi@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601687}
50 files changed