refactor: bcrypt key derivation to aead (#491)

[bizk]

Description

Closes: #3129

• Replaced bcrypt key derivation for argon2id, this approach is secure and resolves most of bcrypt common issues. Algorithm implementation uses these parameters

const (
	argon2Time    = 1 // Recommended by library authors: Uses max memory available
	argon2Memory  = 64 * 1024 // Memory usage 
	argon2Threads = 4
	argon2KeyLen  = 32 // Key bytes
)

• Replaced xsalsa20 symmetric encryption with AEAD ChaCha20Poly
• Added backward compatibility for old keys.
• Added respective tests
• Fixed suggestions and comments by @facundomedica

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🔗 zboto Link

[tac0turtle]

Is this backwards compatible?

[facundomedica]

Looks good, please check the errors in the tests

[bizk]

@tac0turtle > Is this backwards compatible?

Yes it is backward compatible, we check the header of the new method are there otherwise we do things the old way (bcrypt and salsa)

Thanks for reviewing the code @facundomedica

[IdaTucker]

tac0turtle

The change is backwards compatible: as was pointed out to us by Facundo, there is a header field called kdf, which used to be set to bcrypt, and from this change onwards, the kdf field will be set to argon2.
Upon decryption if the field is set to argon2, we use the AEAD, otherwise we fall back to the old way of generating the decryption key and decrypting.