webview: Add cookie headers to shouldInterceptRequest

The problem is that shouldInterceptRequest
gets fired before the net stack ultimately adds the
cookie header. This means that Android developers have to
separately query the cookie manager for headers but as we introduce
new changes to the cookie header, the CookieManager API
can't keep up.

The one issue with this approach is that we are of course
having to try replicate what the network stack would be doing.
In this case, I am matching the partitioning but there
could be other cookie behaviors we need to preserve.
We are somewhat forced to maintain this already for WebView's
restricted cookie manager so we can share the policy which lowers
the maintenance burden a bit.

We also discovered that Set-Cookie doesn't have an effect with
shouldInterceptRequest either for similar reasons.
The Set-Cookie header is not allowed to be persisted over the mojo
calls so we need to return that value to our URL Loader factory with a
simple callback.

Bug: 41496912
Change-Id: Iff5cc37ab0f678c59503cc9d69e3c05cd4ccdf4a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5616051
Reviewed-by: Richard (Torne) Coles <torne@chromium.org>
Commit-Queue: Rupert Wiser <bewise@chromium.org>
Auto-Submit: Rupert Wiser <bewise@chromium.org>
Reviewed-by: Mike Taylor <miketaylr@chromium.org>
Reviewed-by: Dylan Cutler <dylancutler@google.com>
Cr-Commit-Position: refs/heads/main@{#1321072}