RP2040 internal temp as telemetry, fix TCXO voltage. Create New variant Pico Hat for SX1262

[thomasabbott]

Two in one:

1a) Adding telemetry for the RP2040 internal temperature sensor on the waveshare RP2040 lora board.
1b) Fixing the TCXO voltage which can't be zero in RadioLib 7.3.0. Left in some MESH_DEBUG prints used to diagnose this. This may fix #1109.
Not tested on hardware.

2. New variant for the Waveshare SX1262 LoRa Node Module for Raspberry Pi Pico cloning the Waveshare RP2040 Lora and changing the GPIO pins.

Tested pico_hat_sx1262_companion_radio_usb and pico_hat_sx1262_repeater on hardware:

• New temperature telemetry is reported correctly (within the limits of the sensor, so +- 5 degrees)
• on-board LED flashes for LORA Tx

[recrof]

we already have rpi pico w and waveshare rp2040 in variants, is this something different?

also - we use internal temperature sensors for esp32 and nrf52, would be good to use same way of doing things across platforms: #1206

[JDat]

Not sure about new variant, but other thing looks OK. I am also working with RP2040. I want to add SPI selection/config for RP2040 and powersaving by downclocking RP2040 to 12 MHz. Next thing is to experiment with RP2040 sleep modes. All these changes/additions can be done on PicoW variant for now.