Base64StringKeyGenerator should not have a minimum length

[OrangeDog]

Expected Behavior

As with all other StringKeyGenerators and BytesKeyGenerators, developers should be free to choose an output length as small as they wish.

Current Behavior

Throws IllegalArgumentException if keyLength is less than 32.

Context

I want to generate random keys that are reasonably easy for humans to transcribe.
Base64 provides a good balance of usable character set and entropy per character.

However, this forces a minimum of 43 characters (⌈ 32 * 4/3 ⌉), which is unreasonable for human use.

[OrangeDog]

It may also be a bug that keyLength is not the actual length of the key, but the pre-encoded length.