Allow passing JsonSerializerSettings to OpenApiExampleResolver

Currently, we can pass naming strategy to the Resolve() methods, but I have additional settings (e.g. custom converters) I would like to use for generating examples.

I feel it would be handy to pass serializer settings to resolve, or use JsonConvert.DefaultSettings to get the default settings, which we can set in startup.

Start with OpenApiExampleResolver and its Resolve() methods, then inspect how the naming strategy is passed. Done means callers can provide JsonSerializerSettings for example generation, including custom converters, or the resolver uses JsonConvert.DefaultSettings as described, while existing behavior remains intact.

Written by the indexing model from the issue text.