🐛 Fixes PropagateStop and PropagateOver (#21622)

# Objective

Fixes #21620 

Ensures `PropagateStop` works as documented. At it stands,
`PropagateStop<C>` is described as only preventing it's Children from
inheriting `C` but in practice that entity itself would not inherit `C`.

Makes `PropagateOver` work. It just plain didn't work at all.

## Solution

Adjusted the flow to prevent recursively inheriting `Inherited` when
`PropagateStop` present, as opposed to not accessing `PropagateStop`
entities entirely.

Skips applying `C` when `Inherited<C>` and `PropagateOver<C>` are on the
entity.

## Testing

I updated the tests first to verify the test cases. They were incomplete
and didn't pass once checking for the proper end state.

After verifying those were not functioning, trimmed and adjusted code
until it functioned.

## Fuller Explanation

To my understanding of the goals (and my implementation) the idea is
that the result of these components would be like

```
(Propagate<C>, Inherited<C>, C)
  (Inherited<C>, C)
    (PropagateOver<C>, Inherited<C>)
      (Inherited<C>, C)
        (PropagateStop<C>, Inherited<C>, C)
```

While the previous (incorrect by my measure) appeared to be

```
(Propagate<C>, Inherited<C>, C)
  (Inherited<C>, C)
    (PropagateOver<C>, Inherited<C>, C)
      (Inherited<C>, C)
        (PropagateStop<C>)
```

So of note: The `PropagateOver<C>` is still getting `Inherited<C>` in
this current adjustment. I believe it was doing that before, but I
didn't fully understand the reasoning for the `Inherited<C>` at all? I
guess it's to properly mark that the `C` is an inherited one, so maybe I
do need to remove it on `PropagateOver<C>` as well, to ensure cleanup
doesn't also remove any separately applied `C`?

I didn't look closely at what all the other tests are attempting to test
(or if they are correctly testing those) to evaluate if other changes
need to be made.

if `PropagateOver<C>` doesn't have `Inherited<C>` and is reparented,
would it be simple to ensure that its children have their `Inherited<C>`
removed/updated properly?

Looking at the code more, chances are this can be simplified a lot with
the use of AncestorIter and DescendentIter, but I am not sure if jumping
into a fuller refactor makes sense at this moment as opposed to
attempting to fix this immediate issue and following up with a bigger
refactor?

thoughts?

---------

Co-authored-by: robtfm <[email protected]>

Author: ekwoka