Add ability to interpret primary constructor arguments without annotations as not required properties

[altro3]

By config property micronaut.openapi.constructor-arguments-as-required

Fixed #2116

[altro3]

@graemerocher @sdelamo I don't know why they initially did the opposite, that arguments in the primary constructor are mandatory. In general, this is not a correct interpretation, because the presence of an argument in the constructor does not make it mandatory, unless an explicit @NonNull annotation is specified.

But to make sure no one breaks anything, I added the ability to softly switch the interpretation of arguments without annotations for those who use this feature.

[anna-geller]

@altro3 big thanks for the PR, this will also solve the issue on our side at Kestra.

Hi @graemerocher @sdelamo, could you review the PR sometime soon-ish or ask some other maintainers? We're also blocked due to this issue. We're working on an SDK and due to this bug, our models are not correctly generated. We'd kindly appreciate it if you could get that reviewed and merged. Thanks so much in advance!

[altro3]

@graemerocher ping