BlockDevice trait

[qwandor]

Hello,
How would folks feel about the addition of a 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. Unlike the other traits in embedded-storage it would only allow access to whole blocks. It would also avoid the 4 GiB size limit the other traits have due to using u32 addresses.

I originally proposed this for the embedded-io crate, but they suggested that this crate might be a better fit. If this seems like a reasonable place for it I'm happy to send a PR to discuss the details.