Implement a validation/customization mechanism fault injection on each target pod

[pablochacin]

Before injecting a fault in a target pod, there are some validations that are required to prevent unexpected results. Also,

• Validate target port when injecting protocol faults to Pods #128
• Warn about, or prevent users from disrupting pods with hostNetwork #216

Also, in some cases some information about the target pods is needed to adapt the fault injection to each target:

• Use Enpoints to find ServiceDisruptor's targets #131
• Automatically exclude liveness/readiness probe endpoints #195

Therefore, it would be convenient to devise a generic mechanism for processing each target during the fault injection that allows validations it and also adapting the fault injection to each target.