[Variant] `impl FromIterator` fpr `VariantPath`

[alamb]

Should it also impl FromIterator so people can do:

VariantPath::from_iter(["foo".into(), 0.into()])

or

["foo".into(), 0.into()].into_iter().collect::<VariantPath>()

Originally posted by @scovich in #7942 (comment)

[sdf-jkl]

take