fix(t1000e): reclassify P0.04 as sensor power enable GPIO (#9826)

P0.04 is a digital power-enable pin for the NTC/LUX sensors, not an ADC
input. The old code was calling analogRead() on a floating GPIO that
happened to read ~mid-rail, coincidentally producing reasonable
temperature values.

- Rename T1000X_VCC_PIN to T1000X_SENSOR_EN_PIN and drive it HIGH in
initVariant() for both T1000-E and T1000-S variants
- Read BATTERY_PIN (with ADC_MULTIPLIER) instead, clamped to the 3.0V
LDO output (NTC_REF_VCC) for the NTC resistance calculation

variants/nrf52840/tracker-t1000-e/variant.cpp

@@ -38,6 +38,9 @@ void initVariant()
     pinMode(PIN_3V3_ACC_EN, OUTPUT);
     digitalWrite(PIN_3V3_ACC_EN, HIGH);
 
+    pinMode(T1000X_SENSOR_EN_PIN, OUTPUT);
+    digitalWrite(T1000X_SENSOR_EN_PIN, HIGH);
+
     pinMode(BUZZER_EN_PIN, OUTPUT);
     digitalWrite(BUZZER_EN_PIN, HIGH);