Move Jinja2 template to separate boards.jinja2 file

esphome/components/rp2040/boards.jinja2

@@ -0,0 +1,25 @@
+# Auto-generated by generate_boards.py — do not edit manually
+# To regenerate: python esphome/components/rp2040/generate_boards.py <arduino-pico-path>
+
+# arduino-pico maps pins >= {{ cyw43_gpio_offset }} to CYW43 wireless chip GPIOs
+CYW43_GPIO_OFFSET = {{ cyw43_gpio_offset }}
+CYW43_MAX_GPIO = {{ cyw43_max_gpio }}
+DEFAULT_MAX_PIN = {{ default_max_pin }}
+
+RP2040_BASE_PINS = {}
+
+RP2040_BOARD_PINS = {
+{%- for name, pins in board_pins %}
+    {{ name | repr }}: {{ pins | format_pins }},
+{%- endfor %}
+}
+
+BOARDS = {
+{%- for name, info in boards %}
+    {{ name | repr }}: {
+    {%- for key, value in info.items() %}
+        {{ key | repr }}: {{ value | repr }},
+    {%- endfor %}
+    },
+{%- endfor %}
+}