std/crypto: properly support arbitrary output sizes

[jedisct1]

Fixes#7657

[LemonBoy]

According to RFC7693 the following output lengths are defined:

Algorithm | Target | Collision | Hash | Hash ASN.1 |
Identifier | Arch | Security | nn | OID Suffix |
---------------+--------+-----------+------+------------+
id-blake2b160 | 64-bit | 2**80 | 20 | x.1.5 |
id-blake2b256 | 64-bit | 2**128 | 32 | x.1.8 |
id-blake2b384 | 64-bit | 2**192 | 48 | x.1.12 |
id-blake2b512 | 64-bit | 2**256 | 64 | x.1.16 |
---------------+--------+-----------+------+------------+
id-blake2s128 | 32-bit | 2**64 | 16 | x.2.4 |
id-blake2s160 | 32-bit | 2**80 | 20 | x.2.5 |
id-blake2s224 | 32-bit | 2**112 | 28 | x.2.7 |
id-blake2s256 | 32-bit | 2**128 | 32 | x.2.8 |
---------------+--------+-----------+------+------------+

And we're not exporting/testing the nn=160 variant of both the blake2 hashes.

Shall we add the two missing definitions and a test?

[jedisct1]

160 and 224 bits are uncommon settings, but sure, having it doesn't cost much and can be useful, if only to spot bug like these.

I'm going to add tests and types for nn=160.