Rename IInheritable::InsertParent to improve clarity of intent

[lhecker]

This is a followup commit for 168d28b.
By renaming IInheritable::InsertParent(com_ptr) and
InsertParent(size_t, com_ptr) into AddLeastImportantParent(com_ptr)
and AddMostImportantParent(com_ptr) respectively, we can improve
the clarity of our code's intent without the need for comments.

PR Checklist

• I work here
• Tests added/passed

[miniksa]

I'm not sure I understand the parenting and priorities well enough to reason whether this is clearer or not. There's both a parent/child tree and an importance value assigned to each of them depending on whether they're push_front or push_back'd into the list of parents? Yes?

[lhecker]

Yeah you could also call it PushParentBack and PushParentFront.
I prefer this renamed version for 2 reasons:

• It's agnostic over the underlying container. The current API practically only works with a std::vector. But what if we want to reverse it, to have the most important one at the end?
• Currently the code only calls either exactly InsertParent(somePointer) or InsertParent(0, somePointer). The positional parameter is actually never really used and thus can be replaced with something that's a bit more explicit.

[lhecker]

I think the correct term for our inheritance tree is a "ordered anti-arborescence" -- a directed acyclic graph, where lists of paths are ordered and there's only one path at most between any 2 vertices.

The ordering is important, because if a settings item doesn't exist the "first" parent that has it set will win and return the value. That way the base layer is preferred over the defaults.

[carlos-zamora]

Thank you!!!

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