drivers: lora: sx126x: Support fine-grained STM32WL PA config

Add STM32WL-specific sx126x_set_tx_params function based on the
STM32CubeWL modifications to LoRaMac-node.

Add the "power-amplifier-output" DT property to
"st,stm32wl-subghz-radio" for selecting between the RFO_LP and RFO_HP
output configurations provided by the above mentioned function.

Add the "rfo-lp-max-power" and "rfo-hp-max-power" DT properties for
defining the maximum design power of the respective outputs' matching
networks.

closes #48511

Signed-off-by: Kenneth J. Miller <ken@miller.ec>