feat(mssql): add md2 and md4 hashbytes algos

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Description of changes

Adds non-auto computed documentation example for hashbytes.

Also adds support for MD2 and MD4 hashing algorithms for Microsoft SQL Server's HASHBYTES function.

Technically, quoting from the docs:

Beginning with SQL Server 2016 (13.x), all algorithms other than SHA2_256, and SHA2_512 are deprecated.

Not sure if it's worth including this portion of the change or not.

In [2]: ibis.options.interactive = True

In [3]: str_lit = ibis.literal("Hello, world!")

In [4]: str_lit.hashbytes("md2")
Out[4]: 
┌──────┐
│ None │
└──────┘

In [5]: str_lit.hashbytes("md4")
Out[5]: 
┌───────────────────────────────────────────────────────┐
│ b'\n\xbe\x9e\xe1\xf3v\xca\xa1\xbc\xec\xad\x90B\xf1ns' │
└───────────────────────────────────────────────────────┘