seeed_xiao_nrf52840_kit improvements (#6930)

* feat: seeed_xiao_nrf52840_kit improvements
- LEDs:
  - Change RGB LED to be active low as it is common anode
  - Remove re-definition of LED_PIN
  - Use red LED to indicate flash writes
  - Use blue LED as user LED (External Notification module)
- GPIO: Re-word unused BUTTON_PIN comment
- Wire: Set I2C pins to match XIAO nRF52840 Sense's LSM6DS3TR IMU
- Battery:
  - Use charge LED to detect charging state
  - Move voltage divider boilerplate out of src/main.cpp and into initVariant()
  - Fix dependencies for above in related XIAO BLE DIY variants

Build tested variants:
- seeed_xiao_nrf52840_kit
- xiao_ble
- seeed-xiao-nrf52840-wio-sx1262

Flashed to and tested on hardware:
- seeed_xiao_nrf52840_kit

Signed-off-by: Andrew Yong <me@ndoo.sg>

* chore(seeed_xiao_nrf52840_kit): Re-order generic GPIO definitions

Signed-off-by: Andrew Yong <me@ndoo.sg>

* chore: Use ADC_CTRL for XIAO nRF52840

Signed-off-by: Andrew Yong <me@ndoo.sg>

---------

Signed-off-by: Andrew Yong <me@ndoo.sg>

variants/xiao_ble/variant.cpp

@@ -52,4 +52,11 @@ const uint32_t g_ADigitalPinMap[] = {
 
     // VBAT
     31, // D32 is P0.10 (VBAT)
-};
+};
+
+void initVariant()
+{
+    // Set BQ25101 ISET to 100mA instead of 50mA
+    pinMode(HICHG, OUTPUT);
+    digitalWrite(HICHG, LOW);
+}