Make metadata use EditorPropertyVariant in the inspector

[YeldhamDev]

What problem(s) does this PR solve?

This PR makes so that metadata properties use EditorPropertyVariant. This allows to change their type without the need to delete and recreate them.

[KoBeWi]

#113678

[YeldhamDev]

Crap, didn't notice your PR, sorry.

The way you handled the PropertyInfo is way better than my hack, but I'm not so sure about the way the variant list was handled. Even if a little more convoluted, I think it's more future-proof to add a way to set the exceptions and renames.

[KoBeWi]

Even if a little more convoluted, I think it's more future-proof to add a way to set the exceptions and renames.

Yeah, but my workaround is very minimal, so it's easy to replace if needed. And we won't need to change it probably until major Variant changes, which are still rather far away.

[YeldhamDev]

Ehh, very well. That PR needs to be rebased, though.