[java] improve petstore tests with openapi v3 spec (#16447)

* regenerate tests in jersey2-java8 client

* update samples

* fix java google api client tests

* update java resteasy to use v3 spec for tests

* update java vertx to test with v3 spec

* update java resttemplate to test with v3 spec

* add new files

* regenerate jersey1 tests

samples/client/petstore/java/resttemplate-withXml/docs/NullableClass.md

@@ -0,0 +1,24 @@
+
+
+# NullableClass
+
+
+## Properties
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+|**integerProp** | **Integer** |  |  [optional] |
+|**numberProp** | **BigDecimal** |  |  [optional] |
+|**booleanProp** | **Boolean** |  |  [optional] |
+|**stringProp** | **String** |  |  [optional] |
+|**dateProp** | **LocalDate** |  |  [optional] |
+|**datetimeProp** | **OffsetDateTime** |  |  [optional] |
+|**arrayNullableProp** | **List<Object>** |  |  [optional] |
+|**arrayAndItemsNullableProp** | **List<Object>** |  |  [optional] |
+|**arrayItemsNullable** | **List<Object>** |  |  [optional] |
+|**objectNullableProp** | **Map<String, Object>** |  |  [optional] |
+|**objectAndItemsNullableProp** | **Map<String, Object>** |  |  [optional] |
+|**objectItemsNullable** | **Map<String, Object>** |  |  [optional] |
+
+
+