crypto: Small optimizations of BCrypt

[BiiChris]

Changes made:

• Removed unecessary encoding and decoding between salt generation and expensiveblowfishsetup.
• Magic cipherdata added directly into bcrypt function
• Test salt unencoded since expensiveblowfishsetup no longer needs to unencode salt

These changes make no difference to time taken for entire algorithm due to the time spent is entirely on hashing, but it did lead to about 20% less allocations/operation on benchmarks. The size of these allocations are likely negligible compared to the total memory consumption, but nonetheless an improvement.

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