resolveTypeArgument previously fell through to Object for a WildcardType,
so a wildcard nested inside a forwarded supertype argument (e.g.
extends Base<List<? extends Number>>) lost its bound. Resolve it to its
upper bound, mirroring getNestedTypeData, so a type variable inside the
bound is still substituted against the current context.

Adds a TypeData unit test for the bound resolution and a discriminated
POJO round-trip (ForwardingWildcardModel) that fails without the fix.

JAVA-6065

The two newInstance overloads duplicated near-identical type-argument
walking. resolveTypeArgument is a strict superset of getNestedTypeData
(with an empty context, type variables erase to Object exactly as
before), and it also fixes a latent ClassCastException when a wildcard's
upper bound is itself parameterized (e.g. ? extends List<String>).
Delegate the two-arg newInstance to it and remove getNestedTypeData.

JAVA-6065