Rename kCtap to kCtap2 to disambiguate from future standards

Change-Id: I0cd5347fbb838002d168d113cf409bd9d0f040e1

In lieu of biometric registration implementation, we need a
way to disambiguate CTAP2.1Pre from 2.0. This CL simply
renames kCtap to kCtap2 so that a future CL adding support
for 2.1Pre (currently WIP) won't be as large.

Change-Id: I0cd5347fbb838002d168d113cf409bd9d0f040e1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1616451
Reviewed-by: Martin Kreichgauer <martinkr@google.com>
Reviewed-by: Kim Paulhamus <kpaulhamus@chromium.org>
Commit-Queue: Matthew Webb <noviv@google.com>
Cr-Commit-Position: refs/heads/master@{#661839}
21 files changed