Disambiguate _bleio Native from _bleio HCI

[eightycc]

From PR #9878 @dhalbert suggests:

Suppose _bleio for HCI was actually called _bleio_hci. The libraries would do something like:

try:
    import _bleio
except ImportError
    import _bleio_hci as _bleio

Conceivably, one could make a build that would support both, though it's not of much use (though there are compile issues about that, so you don't have to duplicate the shared-bindings code).

[dhalbert]

I am not sure this is a good idea at all, and I'd say don't bother with a PR for this right now.

[tannewt]

I'm also not sure this is the best way. I think in the future _bleio will build on one BLE host stack (Zephyr) that we can configure with an HCI transport. Native BLE will then make it available as board.BLE or something.

[dhalbert]

Let's close this as not planned.