[OOBE][QuickStart] Add SecondDeviceAuthBroker

Adds SecondDeviceAuthBroker to TargetDeviceBootstrapController and
implements the first step of the attestation flow - getting the
challenge bytes from Gaia and sending it to the phone.

Bug: b:283964058
Change-Id: I64e84a419bc146d7f093f3565336b03ae3525860
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4608309
Reviewed-by: Kush Sinha <sinhak@chromium.org>
Commit-Queue: Renato Silva <rrsilva@google.com>
Cr-Commit-Position: refs/heads/main@{#1161136}