cryptotoken: remove support for non-proxied mode.

For some time cryptotoken has forwarded requests to Webauthn by default.
Since this has been stable for a while now, remove the feature flag and
all the code from cryptotoken that dealt with communicating with security
keys directly.

This leaves cryptotoken as a legacy shim for Webauthn and, as such, we
no longer worry about keeping it closure-clean and just delete the
BUILD.gn.

Change-Id: Ic6578f109b2facbc89ea7bc8fc1420870fb7dc6c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1588752
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Adam Langley <agl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#656916}
30 files changed