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.

[thekurtovic]

It fits in pretty nicely without too much changes to the code base. It would be good to add support for anyone who may want to use the feature. What do you think?
h2zero/esp-nimble-cpp@master...thekurtovic:esp-nimble-cpp:feat-multi-conn

Could actually omit setCommonGapFactor and let the application handle it, similar to setting up the ble_gap_multi_conn_params struct.
It's mainly having it piggyback off existing code in NimBLEClient::connect and NimBLEClient::handleGapEvent that matters.
Also should probably be 3 separate PRs since I change some other stuff too.

[h2zero]

Looks nice for sure 👍 would sadly need to wrap it with all kinds of #ifdefs though. Would not be supported in NimBLE-Arduino or older IDF versions.

[thekurtovic]

Where are you seeing spots which would require additional preprocessor use?
I just pushed a commit and it's now just a single block in NimBLEClient
Simply checking for CONFIG_BT_NIMBLE_OPTIMIZE_MULTI_CONN should be all that is required.

// ESP32-C5/C6/C61/H2 only
# if !defined(CONFIG_BT_NIMBLE_OPTIMIZE_MULTI_CONN)
#  define ble_gap_multi_conn_params void
#  define ble_gap_multi_connect(a, cb, ptr) 0
# endif

[h2zero]

Good call, that works too 👍