refactor: Remove static CDC ACM logging nodes.

* To avoid spurious CDC ACM instances when usint CDC ACM for something
  other than logging, move to the approach used by Zephyr of using a
  snippet to redirect console output to a CDC ACM node added by the
  snippet. Remove all the existing static CDC ACM nodes.
* Add new `zmk-usb-logging` snippet that mirrors the upstream
  `cdc-acm-logging` snippet, but still does our extra USB logging
  configuration.
* Updated logging docs accordingly.

Co-authored-by: Cem Aksoylar <caksoylar@users.noreply.github.com>

app/boards/adafruit_kb2040.overlay

@@ -4,6 +4,4 @@
  * SPDX-License-Identifier: MIT
  */
 
-#include "usb_console.dtsi"
-
 &pro_micro_serial { status = "disabled"; };