Adding support for Ikoka Stick with Seeed Xiao nRF54 baseboard.

Adds a new variant 'ikoka_stick_nrf' and associated support files. This is
based on the Xiao nRF54 code with pin numbers and functions changed to suit the
differences in hardware between the WIO SX1262 board and the Ikoka Stick.

Sets the default LoRa transmit power to 9dBm to avoid burning up the frontend
in Ikoka Sticks equipped with the Ebyte 33dBm S22 module on first boot.

Adds support for an SSD1306 display connected to the display header. Note the
display pinout is the same as the RAK4631 display header so make sure to use a
display wired accordingly (aliexpress etc. SSD1306s typically have Vcc & GND
reversed from what this board expects).

Adds support for display rotation to SSD1306Display via a platformIO define.
This support was added following the same paradigms found elsewhere in the code
for rotating a display.

src/helpers/ui/SSD1306Display.cpp

@@ -7,6 +7,9 @@ bool SSD1306Display::i2c_probe(TwoWire& wire, uint8_t addr) {
 }
 
 bool SSD1306Display::begin() {
+  #ifdef DISPLAY_ROTATION
+  display.setRotation(DISPLAY_ROTATION);
+  #endif
   return display.begin(SSD1306_SWITCHCAPVCC, DISPLAY_ADDRESS, true, false) && i2c_probe(Wire, DISPLAY_ADDRESS);
 }