Make other Tornjak backend arguments configurable about tornjak

[maia-iyer]

During conversation with @mrsabath we came to the decision that the extra configurable arguments will live in the Tornjak config as so:

server {
  http {
    enabled = true
    listen_port = "10000"
  }

  tls {
    enabled = true
    listen_port = "20000"
    cert = "sample-keys/tls.pem"
    key = "sample-keys/key.pem"
  }

  mtls {
    enabled = true
    listen_port = "30000"
    cert = "sample-keys/tls.pem"
    key = "sample-keys/key.pem"
    ca = "sample-keys/rootCA.pem"
  }
}

plugins {
  DataStore "sql" {
    plugin_data {
      drivername = "sqlite3"
      filename = "/run/spire/data/tornjak.sqlite3"
    }
  }

}

In this case, instead of calling the backend executable three times, the executable will open three connections itself.

I have opened PR #176 to implement this