Don't panic on full bluetooth receive queue

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https://github.com/esp-rs/esp-wifi/blob/c446177984b82b5e1658d6b24318e7214460ded8/esp-wifi/src/ble/btdm.rs#L94

The above line calls unwrap(), which causes a panic if enqueue was called while the queue was full. The queue just overwrites the oldest item and returns that item as the Err. This should mean a packet is dropped, it shouldn't mean the whole program panics in an unrecoverable way.

[bjoernQ]

Good point! It's definitely better to drop a packet instead of panicking