Extract common dbus files and biod client

This CL:
* Moves chromeos/dbus/constants/attestation_constants to their proper
  BUILD.gn file.
* Removes an unnecessary dependency on //chromeos/dbus from
  //chromeos/dbus/system_clock
* Moves some shared dbus files to a //chromeos/dbus:common component
* Extracts biod files to //chromeos/dbus/biod which only depends on
  //chromeos/dbus:comon, not all of //chromeos/dbus.

This will be necessary to extract additional clients from
//chromeos/dbus.

Bug: 647367
Change-Id: I2628b8e52bef24143d0ae740a26924b5b255be36
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1531223
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642198}
11 files changed