Add compile-verified test fixture for the new GDEY029F51 driver

tests/test_gxepd2_290c_gdey029f51.esp32-idf.yaml

@@ -0,0 +1,25 @@
+esphome:
+  name: gxepd2-test-290c-gdey029f51
+esp32:
+  board: esp32dev
+  framework:
+    type: esp-idf
+external_components:
+  - source:
+      type: local
+      path: ../components
+    components: [gxepd2]
+spi:
+  clk_pin: 18
+  mosi_pin: 23
+logger:
+display:
+  - platform: gxepd2
+    model: GxEPD2_290c_GDEY029F51
+    cs_pin: 5
+    dc_pin: 17
+    reset_pin: 16
+    busy_pin: 4
+    update_interval: 60s
+    lambda: |-
+      it.fill(Color::WHITE);