Add esp32 ble_scan example.

[elrom]

No description provided.

[elrom]

Interestingly, at least on my board (esp32s3), I'm not getting any results from the scan. @lulf any thoughts?

[lulf]

@elrom I've only tested it on nrf, so maybe an esp-specific thing yeah. I'll try to test this on my esp32c3 and see if I can find anything.

[lulf]

@elrom Seems like there is someone who got it to work after making L2CAP_MTU configurable in the example, is you make that modification I'd be happy to merge this PR (ref #288)

[Meigs2]

Yes, all you have to do is pass in a const generic for the run method, pub async fn run<C, const L2CAP_MTU: usize>(controller: C) and use that const instead of the hardcoded one in the example. This will require modification to the other examples to pass in a value for L2CAP_MTU to get them to compile.