Add `BlockDevice` trait to embedded-io

[qwandor]

Hello, Would the embedded-io crate be a good home for a common BlockDevice trait, something like the one from embedded_sdmmc? This would be a common interface between things like SD card drivers, VirtIO block devices and so on, and crates which provide filesystem implementations on top of a block device. If this seems like a reasonable place for it I'm happy to send a PR to discuss the details.

[Dirbaio]

maybe embedded-storage is a better place?

(and maybe we should adopt (parts of?) the embedded-storage crate into this repo and make it officially WG-endorsed?)