Blecon Device SDK v1.2.0

New functionality

• New large request examples
• Update nRF Connect SDK to v2.7.0
• Add nRF52833 DK support for Zephyr and nRF5 SDK examples

Fixes

• Fix handling of no L2CAP credit being available in Zephyr port
• Fix a session re-negotiation issue leading to an increase in request failures
• Clarify maximum sizes in docs for request parameters and data frames