[Port to 2.x]: feat: mTLS support (#27534)

Port master-1.x commit https://github.com/influxdata/influxdb/commit/3cbe3e62dc to main-2.x.

Adds client certificate verification (mutual TLS) to the HTTPS listener. 2.x has no pkg/tlsconfig; server-side support needs to be implemented in the launcher TLS setup (ClientAuth / ClientCAs on the server tls.Config, new tls-client-* flags). The opentsdb, subscriber and client/v2 parts have no 2.x equivalent.