[v1.20.0.rc9] Firmware release candidate

### Improvements:
- Releasing GIL when ssl handshake is performed.
- Allow PDN list update when carrier is defined in LTE
- Add support for LTE modem responses greater than UART buff size
- Added Check for LTE band support against both SW and HW versions of the LTE modem.
- Updated Sqns upgrade scripts to v1.2.5
### Bug Fixes:
- Enabling Access to 2nd SPI perf for GPY modules
- Use Hardware timers for Lora timer tick to fix RTOS timer drifts when cache is disabled.
- Updated OTA fixing failing OTAs after switching to Factory Partition.
- Fix crash when pin ISR handler fires (i.e. LoRa TX done) during flash operation PR #278 by Martijn Thé  @martijnthe
- Remove defaulting of wifi max_tx_pwr  to level 20 in init()
- modlora: Reverted the rx spread factor in stats

esp32/pycom_version.h

@@ -10,7 +10,7 @@
 #ifndef VERSION_H_
 #define VERSION_H_
 
-#define SW_VERSION_NUMBER                              "1.20.0.rc8"
+#define SW_VERSION_NUMBER                              "1.20.0.rc9"
 
 #define LORAWAN_VERSION_NUMBER                         "1.0.2"