Revert of Add U2F request state machines (patchset #5 id:180001 of https://codereview.chromium.org/2821263005/ )

Reason for revert:
Reverting because U2fRequestTest.TestBasicMachine fails consistently on MSan bots (Linux MSan, Linux ChromiumOS MSan).

Original issue's description:
> Add U2F request state machines
>
> U2fRequest base class is extended by each type of U2F
> request. Common functions of enumeration and device iteration
> are defined in the base class. U2fSign performs an entire
> sign request on any attached U2F devices, and U2FRegister
> performs the registration request on the devices.
>
> BUG=686310
>
> Review-Url: https://codereview.chromium.org/2821263005
> Cr-Commit-Position: refs/heads/master@{#466529}
> Committed: https://chromium.googlesource.com/chromium/src/+/892eb34117f811aa62c821c9129dc53110266e9a

TBR=reillyg@chromium.org,kpaulhamus@chromium.org,juanlang@chromium.org,piperc@google.com,piperc@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=686310

Review-Url: https://codereview.chromium.org/2838573002
Cr-Commit-Position: refs/heads/master@{#466666}
17 files changed