Setup ScyllaDB with mTLS for node to node communication

[tnozicka]

Is this a bug report or feature request?

• Feature Request

What should the feature do:
We need to setup ScyllaDB with node to node mTLS to make sure the node communication on our shared platform is encrypted and authenticated.

This also prevents nodes to accidentally join a different cluster which can happen when there is no authentication and IPs are eventually reused. (If dc name matches.)

We should enable node-to-node encryption by default and only have fallback option to use insecure one instead.

https://docs.scylladb.com/stable/operating-scylla/security/node-node-encryption.html

Tasks

Beta Give feedback

1. Create enhancment proposal for node to node mTLS #1374
   kind/design priority/important-soon +2
2. Implement automatic node to node mTLS to secure the communication #1375
   kind/feature priority/important-soon triage/accepted +3
3. Benchmark performance with node-to-node mTLS enabled #1376
   kind/epic priority/important-longterm triage/accepted +3