We should reconsider network configuration

[scholzj]

When using StrimziKafkaCluster, we seem to always create new network. That seems to lead to problems as Docker can have only a limited number of networks and when you run out of it, you get an error such as in #80. We should consider how we deal with this:

• Add an option to configure the network to be used (e.g. shared network works around the issue in StrimziKafkaCluster.start() seems to silent criticial errors #80)
  • If we decide to do this, we should consider how to do it
    • Should we expose the Network object from Test container?
    • Should we have just some flag to (e.g. boolean sharedNetwork) to not expose TestContainer details into the user application?
    • Should an environment variable be used to avoid setting it easily differently for different environments?
• Or should we just rely on the defaults from Test Container? The KindContainer does not seem to do anything with network (but we do not start/stop it as often as we do for the Kafka container)