Add data encryption/decryption API to Wallet class

[ozyman42]

Context

Many potential applications might prefer to encrypt end user data via a public key the user controls rather than encrypting via a user's password (i.e. lastpass), as passwords are a poor UX compared to a web 3 wallet. Metamask currently is the only web 3 wallet I'm aware of which offers the ability to decrypt via private key. Ideally Solana wallets should support this, and ideally all the wallets would use the same algorithm for obtaining a public encryption key and the same asymmetric encryption algo too. In the linked EIP you see a proposal for wallets to offer an RPC for encryption via secp256k1 + ECIES.

Proposal: Add data encryption and decryption methods to the SDK's Wallet class

Relevant Links

Relevant issues opened in web3.js and in Backpack:

• Solana web3.js: Create data encryption/decryption standard plus supporting APIs for wallets to implement solana-labs/solana-web3.js#1367
• Backpack: Add methods for encrypting via public key and decrypting via private key coral-xyz/backpack#4241

Similar discussion in Etheruem: https://ethereum-magicians.org/t/eip-5630-encryption-and-decryption/10761/128

Metamask SDK:

• encrypt: https://docs.metamask.io/wallet/reference/eth_getencryptionpublickey
• decrypt: https://docs.metamask.io/wallet/reference/eth_decrypt/