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Primarily an interface-only change. Only change past the interface level
of the stack was to internally pass rawer information rather than
use RequestInfo as that struct is specific to the old Resolve API.

Only handles the basic case for now (HostPortPair input without any
significant options), but additional funtionality will be added in
subsequent changes.

Copy and convert all the unittests that can be implemented using the new
method with its current basic functionality. If we ever convert all
usage to the new method and delete the old, we'll be able to cleanly
delete all the old tests.

Design doc:
https://docs.google.com/document/d/1NmADJX00oRe9TxFCJTWl8ofdfyR22pbKT8-5Ad5lBsU

Bug: 821021
Cq-Include-Trybots: luci.chromium.try:linux_mojo;master.tryserver.chromium.android:android_cronet_tester;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I4fe454761e2930d6f235e8e505b689f8917fdeed
Reviewed-on: https://chromium-review.googlesource.com/1099427
Commit-Queue: Eric Orth <ericorth@chromium.org>
Reviewed-by: Helen Li <xunjieli@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575065}