feat(RadioInterface): Tx power gain calculation rework (#6796)

- Rename REGULATORY_GAIN_LORA to TX_GAIN_LORA
- Move gain-based Tx power clamping from RadioInterface::applyModemConfig() to RadioInterface::limitPower()
  - User-configured Tx power now matches the Tx power out of the device connector
- Re-order [LoRa Chip]Interface.cpp limitPower() to take place before the final Tx power clamping so we clamp based on the pre-PA Tx power rather than user-configured Tx power

Tested on XIAO BLE variant.

Signed-off-by: Andrew Yong <me@ndoo.sg>
Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

src/mesh/STM32WLE5JCInterface.cpp

@@ -25,11 +25,11 @@ bool STM32WLE5JCInterface::init()
 
     lora.setRfSwitchTable(rfswitch_pins, rfswitch_table);
 
+    limitPower();
+
     if (power > STM32WLx_MAX_POWER) // This chip has lower power limits than some
         power = STM32WLx_MAX_POWER;
 
-    limitPower();
-
     int res = lora.begin(getFreq(), bw, sf, cr, syncWord, power, preambleLength, tcxoVoltage);
 
     LOG_INFO("STM32WLx init result %d", res);