Rotate keys for a given Identifier

[abhi3700]

Currently, as per commit 70348e4 we use the same keypair to generate a new certificate for renewing a given identifier.

But we might have a use case as found in Verified Credentials (VC) notion doc where we need to rotate keys keeping same identifier. The steps would remain same as renew example, but need to use new keypair.

A common application of identifiers is their use in VCs. If a VC is issued to an identifier, as opposed to a public key, it will allow the holder of the VC to rotate their keys, while not needing to renew their VC.

In order to rotate keys for a given identifier, follow the steps below:

1. Generate a new keypair
2. Create a Certificate Manager with the keypair
3. Issue certificate with the same Subject Common Name like test500.
4. Use renewAutoId extrinsic to renew the existing auto id with new certificate.

   💡 New certificate has a new serial no. and new public key info.

Done! 🎉

### Tasks
- [ ] Create a example file: `rotate-keys` in auto-sdk