Support remote key management, encryption, and signing

[andresuribe87]

The SDK should:

• Decouple DID generation from Key Generation.
• Let users of the library bring their signers, likely in the form of an HSM.
• Have key generation be explicitly something that discouraged in production environments.

This would possibly involve:

• Breaking up existing functions into multiple steps.
• Have a standard way to support asynchronous flows with external processes.

[decentralgabe]

Take a look at this for using an AWS or GCP KMS:

• https://github.com/jwx-go/crypto-signer/tree/main/aws
• https://github.com/jwx-go/crypto-signer/tree/main/gcp