Consolidate DefaultBrowserInfo2 and DefaultBrowserStateProvider

This CL makes DefaultBrowserPromo to use DefaultInfoTask to get the
current default browser information, so it can reuse the previous
result instead of fetching the default browser state again.

Bug: 40709747
Change-Id: I9fcf813a9907c35c6c2070fb88e14e839050e5d1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6114428
Reviewed-by: Lijin Shen <lazzzis@google.com>
Reviewed-by: Theresa Sullivan <twellington@chromium.org>
Commit-Queue: Ella Ge <eirage@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1432497}