Add support for secure bundle / SNI (Astra)

[mieslep]

apache/cassandra-gocql-driver#1487 documents a feature request that has been rejected by gocql maintainers as it is certainly a bit messy in the implementation. That code can be found at finn-no/gocql but it is not being kept current with gocql (the last upstream commit was 5378c8f664e946e421b16a490513675b8419bdc7 from August 2020, and there are a large number of merge conflicts to try to bring up-to-date).

The seeming workaround is to use cql-proxy , but it would be great if we could use golang with secure bundles and SNI, as this is a common Kubernetes pattern.

[joao-r-reis]

This would be a request to create a datastax golang driver which would be a separate project imo. This library does contain a very simple client and server but they are not really designed to run in production, they are being used mostly for tests.

[joao-r-reis]

cc @adutra @mpenick @absurdfarce