[OnionSoup] Replace WebConsoleMessage::Level with mojom::ConsoleMessageLevel

This CL
  - removes the nested enum definition WebConsoleMessage::Level, uses
    the mojom one mojom::ConsoleMessageLevel instead everywhere.
  - moves blink/public/web/console_message.mojom into
    blink/public/mojom/devtools/, makes it be able to be used from
    blink/public/mojom/ in the future.

BUG=789854

Change-Id: I94b2b4909b45d83b78c0e03918554813bc97767b
Reviewed-on: https://chromium-review.googlesource.com/c/1420299
Commit-Queue: Leon Han <leon.han@intel.com>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624488}
39 files changed