[daikin_brc] Add sub_unit parameter for multi-unit addressing (#15234)

Co-authored-by: J. Nick Koston <nick@home-assistant.io>
Co-authored-by: J. Nick Koston <nick@koston.org>

tests/components/daikin_brc/common.yaml

@@ -2,3 +2,7 @@ climate:
   - platform: daikin_brc
     name: Daikin_brc Climate
     transmitter_id: xmitr
+  - platform: daikin_brc
+    name: Daikin_brc Climate Unit 2
+    transmitter_id: xmitr
+    sub_unit: 1

tests/components/daikin_brc/test.esp32-idf.yaml

@@ -1,4 +1,3 @@
 packages:
   remote_transmitter: !include ../../test_build_components/common/remote_transmitter/esp32-idf.yaml
-
-<<: !include common.yaml
+  daikin_brc: !include common.yaml

tests/components/daikin_brc/test.esp8266-ard.yaml

@@ -1,4 +1,3 @@
 packages:
   remote_transmitter: !include ../../test_build_components/common/remote_transmitter/esp8266-ard.yaml
-
-<<: !include common.yaml
+  daikin_brc: !include common.yaml