[nextion] Keep add_waveform_data() available without a waveform sensor (#19590)

tests/components/nextion/common_waveform_lambda.yaml

@@ -0,0 +1,8 @@
+# Waveform commands from a lambda with no waveform sensor configured, so
+# USE_NEXTION_WAVEFORM is not defined.
+display:
+  - platform: nextion
+    id: main_lcd
+    lambda: |-
+      id(main_lcd).open_waveform_channel(37, 0, 10);
+      id(main_lcd).add_waveform_data(37, 0, 42);

tests/components/nextion/test-waveform-lambda.esp32-idf.yaml

@@ -0,0 +1,3 @@
+packages:
+  uart: !include ../../test_build_components/common/uart/esp32-idf.yaml
+  waveform_lambda: !include common_waveform_lambda.yaml