This PR addresses the following tickets:

• @DefaultValue value is not cast to the correct type for request parameters #4798
• Why does Schema(description="foo") change generated openapi enum type to type: object?  #4625
• Java attribute of type object is incorrectly mapped to an OpenApi property of type object #4457
• Support arbitrary-type schema (schema without a type) #4014
• [ModelConverters] java.lang.Object is an arbitrary type and should be mapped to an arbitrary type #3834
• BUG @Size annotation is ignored for requestBody parameters of collection type  #4792

Changes include:

• use correct Schema hierarchy for 3.0 and 3.1
• update casting for 3.1
• update object type resolution
• introducing explicit-object-schema and use-arbitrary-schema sys/env props

These 2 properties allow to tweak the processing of Schema type. By default

• for OAS 3.0 a type: object is added whenever any class (even java.lang.Object) is resolved into a schema and no type is defined in annotations or elsewhere. This behavior is unchanged (see below to customize) for compatibility reasons

• for OAS 3.1 type: object is NOT added when type is not defined and there are not Object Schema-specific properties resolved for that schema.

this behavior can be customized by explicitly setting System/Env property explicit-object-schema to true (always add type:object in this scenario or false (don't add type: object)

Additionally, setting use-arbitrary-schema to true allows to customize deserialization behavior (see #4014) to deserialize schemas with no type defined into a ArbitrarySchema with type not defined instead of ObjectSchema with type: object