This is a follow up issue to #26246.

We introduced the --tls-ca flag to most of the commands for Core/Enterprise. We want to add an env var as well to make it easy for people to not have to set the flag on every single invocation, especially if they require a custom CA.

For every single command with this flag:

    /// An optional arg to use a custom ca for useful for testing with self signed certs
    #[clap(long = "tls-ca")]
    ca_cert: Option<PathBuf>,

We need to change it to say:

    /// An optional arg to use a custom ca for useful for testing with self signed certs
    #[clap(long = "tls-ca", env = "INFLUXDB3_TLS_CA")]
    ca_cert: Option<PathBuf>,