ColBytes support for LowCardinality

[jdef]

i'm trying to avoid converting []byte types into string for bulk inserts w/ low-cardinality cols but the API doesn't seem to allow that since []byte is not comparable

as a workaround, I can use ColString and then coerce the []byte vals into string with the unfortunate side-effect of additional allocations. ideally this would not be needed and the API would support low-cardinality w/ []byte natively.

[ernado]

I want LowCardinality for ColBytes too, but I don't know how to fit it to current generic API.

Probably an ad-hoc solution for this specific type would be ok?