Builder Plugin Hook not present for Add Potential Link

[bjeffries]

Describe the bug
The Builder Plugin only works when using an adversary that uses the atomic planner, and does not work when adding a potential link.

This occurs because the Builder Plugin Hook uses the executor.HOOKS dictionary, which is only checked in planning_svc.py (_generate_new_links).
This function is only called by the atomic planner and is never reached when using Add Potential Links.

I will be submitting a PR that address this bug and proposes a better way to approach these hooks in a more flexible manner.

To Reproduce
Steps to reproduce the behavior:

1. Start Caldera with Builder plugin enabled.
2. Add a potential link with a Caldera ability that leverages the Builder plugin.

Expected behavior
The Builder plugin ability should work no matter how it is executed (Add Potential Link or Adversary with Planner).

Screenshots
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Desktop (please complete the following information):

• OS: Ubuntu
• Browser: Firefox
• Version Caldera v4.2 and Caldera v5

Additional context
Add any other context about the problem here.