[udp] Move `on_receive` to const (#9811)

esphome/components/const/__init__.py

@@ -5,5 +5,6 @@ CODEOWNERS = ["@esphome/core"]
 CONF_BYTE_ORDER = "byte_order"
 CONF_COLOR_DEPTH = "color_depth"
 CONF_DRAW_ROUNDING = "draw_rounding"
+CONF_ON_RECEIVE = "on_receive"
 CONF_ON_STATE_CHANGE = "on_state_change"
 CONF_REQUEST_HEADERS = "request_headers"

esphome/components/udp/__init__.py

@@ -1,6 +1,7 @@
 from esphome import automation
 from esphome.automation import Trigger
 import esphome.codegen as cg
+from esphome.components.const import CONF_ON_RECEIVE
 from esphome.components.packet_transport import (
     CONF_BINARY_SENSORS,
     CONF_ENCRYPTION,
@@ -27,7 +28,6 @@ trigger_args = cg.std_vector.template(cg.uint8)
 CONF_ADDRESSES = "addresses"
 CONF_LISTEN_ADDRESS = "listen_address"
 CONF_UDP_ID = "udp_id"
-CONF_ON_RECEIVE = "on_receive"
 CONF_LISTEN_PORT = "listen_port"
 CONF_BROADCAST_PORT = "broadcast_port"