Add option for Variable Get to use a "validation mode"

[Naros]

Description

When a variable is typed as Variant::OBJECT, the underlying variable will initially start being null. This means that users need to be mindful of this and check for this use case in their code. However, rather than adding the need for the users to introduce branch conditions in the graph, an optimized Variable Get node can automatically handle this:

Conceptually, when the variable is null, the node exits the Is Not Valid output pin. If the variable is not null, it exits the Is Valid pin. This avoids the need for using is_instance_valid or null checks for such variables.

Implementation ideas

No response