Allow disabling TLS explicitly

[mieciu]

So we have this logic to ignore creating TLS-based connections when we get specific TLS-related errors (assuming that plaintext connection should be used).

However, when we start Quesma while ClickHouse is dead, aforementioned logic doesn't work and we don't fallback to non-TLS connection properly, as the error is just "connection refused":

So eventually when plaintext ClickHouse comes up, the pool will keep failing repeatedly with tls: first record does not look like a TLS handshake.

The proposed remediation is to just allow explicitly disabling TLS via configuration.

Alternative approach would be to derive this property by looking at port numbers:

• 9000 -> no TLS
• 9440 -> TLS

of course being very verbose in logs about Quesma's choice.