Client Supported Features value not persisted for bonded devices

[piotrnarajowski]

Nimble host currently does not persist the state of the Client Supported Features characteristic for bonded devices across connections. When a bonded client reconnects, any features it previously enabled are reset to default.

According to the Bluetooth Core Specification (Vol 3, Part G, Section 7.2): For clients with a trusted relationship, the Client Supported Features characteristic value shall be persistent across connections.

This affects GATT/SR/GAS/BV-04-C qualification test case

[piotrnarajowski]

@sjanc please add this as parent issue related to #2006

[piotrnarajowski]

This is resolved by #2114 but requires review