Add position and normal reconstruction helper functions.

[jonawals]

Signed-off-by: John [email protected]

What does this PR do?

This PR adds helper functions to reconstruct the view/world position and normal of fragments for Editor Mode Visual Feedback effects that require this information.

How was this PR tested?

This PR has been tested manually in the editor.

[jonawals]

Change looks okay to me but I'm not a shader expert I'm afraid. Is this code used anywhere yet or is the plan to add usage in a separate PR? Thanks!

It's being used in an O3DE blog article for EMVF but is something I have been meaning to put in the toolkit for a while (it's mostly a cannibalization of some existing code in O3DE) 👍