bug: props with optional getters should be validated

Previously in 3.x a class with optional getters was still validated.

This reproducer tests this case, and shows that it currently fails to validate.

If you remove the getter from the POGO, then the test passes.

This was discovered in building the hibernate-reactive guide where we have the following validated DTO:

https://github.com/micronaut-projects/micronaut-guides/blob/ab0bfb2c117de73b24aabbb9422ec58dadaebb8d/guides/micronaut-hibernate-reactive/java/src/main/java/example/micronaut/SortingAndOrderArguments.java

There's a reproducer here: https://github.com/micronaut-projects/micronaut-validation/pull/165

Start with the reproducer in pull request #165 and the validated DTO at guides/micronaut-hibernate-reactive/java/src/main/java/example/micronaut/SortingAndOrderArguments.java. Compare behavior with and without the optional getter, using the prior 3.x behavior as the reference. Done means the DTO with optional getters is validated again.

Written by the indexing model from the issue text.