[core] Add some startup sanity checks for NMs

[WinterSolstice8]

I affirm:

• I understand that if I do not agree to the following points by completing the checkboxes my PR will be ignored.
• I understand I should leave resolving conversations to the LandSandBoat team so that reviewers won't miss what was said.
• I have read and understood the Contributing Guide and the Code of Conduct.
• I have tested my code and the things my code has changed since the last commit in the PR and will test after any later commits.

What does this pull request do?

This PR will inform us of some badly hooked up NMs at startup

This is how I found Peg Powler was missing a PH. I (and others if they want to) will go through this list and fix things in different PRs to reduce the count.

It seems this a mix of misclassified spawntypes, unimplemented NMs and/or unimplemented copies of NMs.

Currently, this PR will only check if the NMs are spawnable. I might have another PR that checks if the phList mobs are not spawnable in any way as well but I think that is less likely.

Steps to test these changes

CI passes

[WinterSolstice8]

#9903 should have reduced the error count by one. rebased.

[WinterSolstice8]

#9906 should also reduce error count by one