Fix MultiRootInheritanceGraph not detecting circular inheritance

[beck-thompson]

MultiRootInheritanceGraph failed to properly detect the case of you being your own parent! This caused an infinite loop on start up of SS14 if you had a prototype whose parent was itself.

Example:

- type: entity
  parent: CoolEntity
  id: CoolEntity

I think the fix is just to add yourself to the data structure before checking for circular inheritance but I could be wrong! You could also just manually check that you don't have yourself as a parent but that seemed hacky. This makes sense and does appear to work.

[beck-thompson]

I uhh think the tests might be borked... The run fine normally on my computer 😢

[deltanedas]

6 hour test real

[beck-thompson]

Figured out the issue with the test. The issue is that the TestCircleException runs and properly detects and throws exceptions. However, because the PrototypeManager is reused over mutliple tests, the graph is all messed up (There are now like partially inserted things that have circular inheritance).

I'm unsure how I should fix this! Here is what I think I could do:
1.) Rewrite the PrototypeManager_Test to not reuse the manager throughout multiple tests.
2.) Change my logic so nothing gets inserted into the graph. I can only think of kind of hard coded checks beforehand so it wont be as pretty!
3.) I had a third I idea... I forget now 😆

For the person reviewing this, or anyone who has an idea 😆, let me know what I should do 🫡

[Tayrtahn]

I'm not an engine maint, but this looks good to me! Just a few suggested tweaks.