Add deriving `public keys` from wallet

**Describe the enhancement**

It would be ideal for the wallet API to generate public keys in the same manner addresses are created. Currently, getting public keys from descriptors seems quite cumbersome as one has to derive the xpub from which they can get a public key. In terms of security, I have not seen any significant breaches related to this.

**Use case**

Generating public keys from a wallet will be useful in multi-sig or taproot setup where a wallet implementation allows users to collaboratively create addresses and perform transactions. Signing is already managed through PSBT.