implement comprehensive LESC and Legacy pairing

[hathach]

Fix #39 , fix #124

NOTE: Although the work is complete, DONT merge this yet. Due to the Arduino IDE 1.8.12 changes, that break the compilation of mixed code for precompiled library Adafruit_nRFCrypto. Which is needed for LESC pairing. We could merge it later when this is issued is resolved and new IDE version is released (and ci re-run passed)

• "Improve precompiled libraries handling" broke "mixed code" libraries arduino/arduino-builder#353
• Fix mixed code precompiled libraries arduino/arduino-cli#611

Copied from changedlog
This version implement comprehensive LESC and Legacy pairing using dynamic & staic Passkey.

• Support static passkey (Legacy only)
• Support LESC on nRF52840 using hardware-accelerated ARM CryptoCell CC310 provided by Adafruit_nRFCypto, therefore nRFCrypto library must be installed
• Rework bonding mechanism to use IRK for peer finding. It is advisable to run clearbonds example to clean up bond files of previous version

BLESecurity

A new class BLESecurity (access with Bluefruit.Security) is added to handle security and pairing.

• setPIN() to set static passkey, this will force to use Legacy Pairing
• setIOCaps() to congiure IO capacities
• setMITM() to enable/disable Man in The Middle protection (passkey), it is auto-enabled when using passkey
• setPairPasskeyCallback() to register callback for displaying pairing passkey to user
• setPairCompleteCallback() to register callback for the result of pairing procedure (succeeded or failed)
• setSecuredCallback() to register callback which invoked when connection is secured. This happens after he pairing procedure is complete, or we re-connect with preivously bonded peer device

For other changes, please check out the changelog for detailed.

[hathach]

e33fa24 revert temporary changes to use latest arduino-cli (which is bundled with Arduino IDE 1.8.12). This will cause ci failed due to above IDE issue. We should wait until it is out, then re-run this PR before merging.

[hathach]

This PR is updated/merged, functionality is tested. Everything seems OK, It should be consider to be ready for merging. Adafruit_nRFCypto is also included as submodule, this is handy since the library can be used by others but still being released together with BSP. This PR uses the mixed precompiled cc310 required Arduino IDE must be updated to 1.8.13