Upgrade TLS version used to connect to registry & blob backend

### What is the version of your Overlaybd

0.6.17

### What would you like to be added?

Upgrade the TLS version to 1.2+.

We found that overlaybd is using TLS v1 to talk to registry & blob backend. We've seen transient failures with S3 that failed on `TLS handshake timeout`. Can we configure overlaybd to use TLS v1.2+?

### Why is this needed for Overlaybd?

Support TLS version 1.2+ in overlaybd.

### Are you willing to submit PRs to contribute to this feature?

- [ ] Yes, I am willing to implement it.