fix: Do not create a Port Forwarding Container instance if auto-discovery does not detect Docker host

[HofmeisterAn]

What does this PR do?

The PR prevents Testcontainers from creating a Port Forwarding Container instance if auto-discovery does not detect a Docker host.

Why is it important?

If users choose to configure their Docker host environment individually using the container builder method WithDockerEndpoint, Testcontainers will throw an exception

Cannot detect the Docker endpoint. [...]

if auto-discovery fails to find a Docker host environment. The port forwarding container depends on auto-discovery and cannot be customized for individual Docker host configurations since it is implemented as a singleton.

To enhance the user experience, we should consider removing feature WithDockerEndpoint. By relying on auto-discovery, we can better support a wide range of features in Testcontainers and simplify test configurations.

Related issues

-

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