* For upcoming ZMK studio work, make a set of rich metadata available
  to provide a friendly name for a behavior, and allow super flexible
  descriptions of the parameters the behaviors take.

* Used for ZMK Studio even remappers to be sure the one
  RPC event listener subscribes to their mapped events.

* Add a new feature for tracking a given behavior by a new concept
  of a "behavior local ID" which is a stable 16-bit identifier for
  a given behavior, that is resilient to new behaviors being added
  and requires no additional work on the part of the behavior
  authors.
* Add implementations for either settings lookup table, or CRC16
  hashing of behavior device names for generating behavior local
  IDs.

* UART and BLE/GATT transports for a protobuf encoded RPC
  request/response protocol.
* Custom framing protocol is used to frame a give message.
* Requests/responses are divided into major "subsystems" which
  handle requests and create response messages.
* Notification support, including mapping local events to RPC
  notifications by a given subsystem.
* Meta responses for "no response" and "unlock needed".
* Initial basic lock state support in a new core section, and allow specifying
  if a given RPC callback requires unlocked state or not.
* Add behavior subsystem with full metadata support and examples of
  using callback to serialize a repeated field without extra stack space needed.

 * Add an easy snippet for enabling USB UART added
   to the `zephyr_udc0` standard node.

* Implement message framing.
* Transports over Web Bluetooth/Serial.
* Message types for serialize/deserialize generated with protoc.

* Add ability to validate a zmk_behavior_binding against
  the behavior metadata available.
* Add keymap API for getting/setting a bindings
  in keymap layers.
* Add settings storage for keymap layer bindings.

* Add APIs for fetching the current keymap, and updating a particular
  binding in a layer of the keymap, including validation of parameters.
* Add API for savings/discarding keymap changes.

* Add bindings to allow creating multiple physical layouts that specify
  their key's physical attributes, and the matching matrix transform
  and dependant kscan to use.
* Synthesize a basic physical layout if none specified, for backwards
  compatibility.
* Update matrix transform API to explicitly pass in the selected transform
  to the API instead of using a fixed chosen transform.
* Move kscan subscription and handling into the physical layout code, so
  that selecting a different physical layout at runtime can also use the
  correct kscan instance.
* Add `physical_layouts.dtsi` file to include so you can use the
  pre-configured `&key_physical_attrs` for adding you layout keys.

* Update our GPIO kscan drivers to more completely support PM device,
  by doing proper hardare init/deinit in the PM action hook.

* Add physical layout definitions for uno and split uno shields.