Add configuration option to `Whisker` and `Goldmane` resource specs to disable creation of default network policies

[benfiola]

While these default network policies help establish a better out-of-the-box security posture, it'd be great if I could disable their creation only so that I can consolidate all of my network policies into a single, auditable location.

Looking at the code, it doesn't seem like a hard thing to implement - and I'd be more than happy to do so if there's agreement that this is a good idea!