[Autofill] Move two functions from AutofillDriver to AutofillClient

This CL moves
- AutofillDriver::IsIncognito() and
- AutofillDriver::GetURLLoaderFactory()
to
- AutofillClient::IsOffTheRecord() and
- AutofillClient::GetURLLoaderFactory().

This is a preparatory CL for moving AutofillDownloadManager
from AutofillManager to AutofillClient: crrev.com/c/4165604.

Bug: 1394786, 892612
Change-Id: Iab3c7d7dccb2ed115f450dcdede9435dc3fa4807
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4180845
Reviewed-by: Peter Beverloo <peter@chromium.org>
Reviewed-by: Dominic Battré <battre@chromium.org>
Commit-Queue: Christoph Schwering <schwering@google.com>
Reviewed-by: John Wu <jzw@chromium.org>
Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1095145}