crypto: blake2b - Reimplement using library API

crypto: blake2b - Reimplement using library API

Replace blake2b_generic.c with a new file blake2b.c which implements the
BLAKE2b crypto_shash algorithms on top of the BLAKE2b library API.

Change the driver name suffix from "-generic" to "-lib" to reflect that
these algorithms now just use the (possibly arch-optimized) library.

This closely mirrors crypto/{md5,sha1,sha256,sha512}.c.

Remove include/crypto/internal/blake2b.h since it is no longer used.
Likewise, remove struct blake2b_state from include/crypto/blake2b.h.

Omit support for import_core and export_core, since there are no legacy
drivers that need these for these algorithms.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20251018043106.375964-10-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>