Reload server TLS certificate from disk

A customer using short-lived TLS certificates would like for a Dolt SQL server to be able to hot reload those certificates from disk when they change. This enables customers to swap the server's certificate without having to restart the server process.

In Go, `tls.Config` structs have a `GetCertificate` member that can be populated with a callback function that can dynamically return the current certificate. This can be combined with code to watch the file system for changes and swap in the new certificate.

Original customer issue: https://github.com/dolthub/dolt/issues/10008