Simplify entity attribute updates

[zehnm]

At the moment one has to use the ucapi.configured_entities.update_attributes method to change an entity attribute.

With the new entity command handler, this is a bit akward. The received entity object should allow direct attribute updates, which also trigger a change event. Directly modifying an attribute on the received entity will not trigger any events.

Proposed changes:

• add an update_attribute method to the entity class
  • either a generic method for all subclassed entities, or a concrete method per entity.
  • for most use cases, a single attribute update is enough. But there are cases where multiple attributes must be updated at the same time, e.g. for light color changes.
    • Either add an additional update_attributes method, or design a single method which allows both.
• changed attributes will trigger a change event

This could then be used in a command handler:

async def switch_cmd_handler(
    entity: ucapi.Switch, cmd_id: str, _params: dict[str, Any] | None
) -> ucapi.StatusCodes:
    print(f"Got {entity.id} command request: {cmd_id}")

    state = None
    if cmd_id == switch.Commands.ON:
        # implement ON logic...
        state = switch.States.ON
    elif cmd_id == switch.Commands.OFF:
        # implement OFF logic...
        state = switch.States.OFF

    if state:
        entity.update_attribute(switch.Attributes.STATE, state)

    return ucapi.StatusCodes.OK