[Core] Add scissor data stack to fix nested clip elements displaying incorrectly

[ambareesh1510]

Fixes #466.

[ambareesh1510]

Hi @nicbarker, sorry for the delay in getting to this! I've currently marked this PR as a draft because I noticed that some of the changes in #450 coincide with the changes in this PR (closeClipElement should be true only if the element is not offscreen -- in fact, I just copy-pasted those two lines from your PR into my code). This change is necessary for my fix to work; would you prefer that I remove it from my PR so that yours can be merged first?

[nicbarker]

👋 Hello, thanks so much for the work here! I'll take a look and then let's get it merged. Totally fine to have those two lines from the other PR in here, we can close out that one 🙂

[ambareesh1510]

Sounds good, I'll mark it as ready for review then.

[nicbarker]

Just letting you know that I'm doing a bit of digging here, because there's a bit of trickyness around floating elements - it's possible to attach floating elements later in the declaration that include a clip rectangle, and as a result we can't rely on visiting them as part of the DFS. I'm sure we can figure something out 🙂

[filippocrocchini]

Hey I found myself implementing almost the same thing to handle custom input, it's nice to know what portion of an element you can interact with when it's partially clipped.

Here's my specific case (context, I am checking against the bounding box, but it would be nice to have a clipped bounding box too)

[filippocrocchini]

This PR doesn't compile in C++ here's what I changed to fix that: d2f2344