Support multi connection optimization

[thekurtovic]

I don't have the required hardware to test this out but seems like it would be a good feature to support.

https://github.com/espressif/esp-idf/blob/master/examples/bluetooth/nimble/ble_multi_conn/ble_multi_conn_cent/tutorial/Ble_Multiple_Connections_Central_Example_Walkthrough.md#multiple-connections

https://github.com/espressif/esp-nimble/blob/d7a585dcf0bff149d92e77ab356d091bdfa45982/nimble/host/include/host/ble_gap.h#L2728-L2764

espressif/esp-nimble@d714e24

[h2zero]

Looks interesting for sure, unfortunately it is vendor specific and not supported upstream by mynewt/nimble so I am reluctant to add support.