[configtls] Bump MinTLS version to 1.3

[mx-psi]

As discussed on a previous Collector SIG meeting, we can bump the default minimum TLS version to 1.3 by default to have a more secure default. Users would still be able to use earlier versions of TLS by modifying the MinTLS configuration.

Since this is potentially breaking, we may want to go through a feature gate process.

Reported as part of the recent security audit.