Split CAs instead of using a single self-signed root CA

[Santti4go]

Feature description

Currently the create_keystore command creates a self-signed root Certificate Authority (CA) and uses it for both Permissions CA and Identity CA through symlink.

This approach creates a limitation in how certificates can be managed. Since basically all three CAs (root, Permissions and Identity) are effectively the same, tasks like updating the permissions.xml policy for a single enclave require access to the root CA's private key, which is not ideal. Similarly, adding a cert.pem for a new enclave also requires the root CA's private key. This setup prevents the delegation of responsibilities between the Permissions and Identity CAs.

I've created a PR with these changes. I targeted the Humble branch as it is the one I'm currently using.
Please feel free to dismiss this issue if this functionality is not desired.