Introduce --test-target to more explicitly declare where tests run

[evgeni]

Why are you introducing these changes? (Problem description, related links)

Using --server-hostname always felt wrong, as we're not actually changing the hostname of the (Foreman) server, just the system we're running the tests against.

What are the changes introduced in this pull request?

• Introduce --test-target which now declares what the server fixture points at
• The old --server-hostname remains if we ever need to change the server name
• Tests still use the server fixture, refactoring this is left for later

How to test this pull request

Steps to reproduce:

Checklist

• Tests added/updated (if applicable)
• Documentation updated (if applicable)

[evgeni]

👀 @jeremylenz

[jeremylenz]

With this in place, it'd be a small change to also support --test-target=localhost for testing deploy-dev setups — just branch on the hostname in get_paramiko_host:

def get_paramiko_host(hostname):
    if hostname == 'localhost':
        return testinfra.get_host('local://', sudo=True)
    return testinfra.get_host(f'paramiko://{hostname}', sudo=True, ssh_config=SSH_CONFIG)

Since deploy-dev already supports --target-host=localhost, this would make the test side consistent with it.

[evgeni]

Sure, if that works that sounds like a good addition