RFR: 8340721: Clarify special case handling of unboxedType and getWildcardType

[Joe Darcy]

On Wed, 25 Sep 2024 22:32:03 GMT, Joe Darcy <darcy at openjdk.org> wrote:

> First piece of a larger set of updates that may be made for JDK-8055219 to clarify the exceptional behavior of `javax.lang.model.util.Types`.

Please also review the CSR [JDK-8340979](https://bugs.openjdk.org/browse/JDK-8340979).

I may augment the regression test to test unions types. Unions types come about from multi-catch statements so getting a hold of one involves a trip with the tree API and not just the standard annotation processing APIs.

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PR Comment: https://git.openjdk.org/jdk/pull/21193#issuecomment-2375386709