Change crypto key logic and add recovery from seed phrase

[mtbitcr]

We are currently using 3 key pairs.
ed25519 for the logic in the DHT.
RSA (2048) for encryption.
secp256k1 for signatures, as well as generating Bitcoin addresses for nodes and bills.

In the latest version of libp2p it is now possible to work with DHT based on secp256k1. Also, the same key pair is used for logic in Nostr. Thus we can reduce the number of keys to two. secp256k1 and RSA.

We can get both of these pairs from the seed phrase. Thus, to fully recover the system, we will only need the seed phrase.

RSA from seed phrase: https://medium.com/@elielmathe/deterministic-rsa-keys-from-mnemonic-seed-key-to-privacy-on-blockchains-for-personal-and-corporate-3102adc3fb42.