refactor testing pass phrase match when enterpring temporary pp

[tomholub]

what does it do?

---

entered pass phrase gets tested against stored keys on this account. It must be able to decrypt at least one key. If it works for at least one, then save it temporarily for use only with that one key.

basically this. Here it creates an array of keys with entered pass phrase

Originally posted by @Kharchevskyi in #323 (comment)

    // append keys to ensure with a pass phrase
        if let passPhrase = passPhrase {
            let keysToEnsure = keysInfo.map {
                PrvKeyInfo(
                    private: $0.private,
                    longid: $0.longid,
                    passphrase: passPhrase
                )
            }

            privateKeys.append(contentsOf: keysToEnsure)

This code should be reworked for clarity

[tomholub]

will be covered in #521