[kotlin] add options sortParamsByRequiredFlag and sortModelPropertiesByRequiredFlag (#4707)

* [kotlin] add option to sortParamsByRequiredFlag

* [kotlin] add option to sortParamsByRequiredFlag

* [kotlin][client] sort parameters in the models

* [kotlin] update docs

* [kotlin][client] simplify sortParamsByRequiredFlag implementation

* [kotlin] experiment with sortnmodel properties by name

* [kotlin] introduce sortModelPropertiesByRequiredFlag

* [kotlin] update docs

* [kotlin] update kotlin

* [kotlin] fix tests

* [kotlin] update docs

* Revert "[kotlin] update docs"

This reverts commit 88ad825de5.

* [kotlin] update docs and petstores

* [kotlin] update docs

* [kotlin] update pet projects

samples/client/petstore/kotlin-nullable/docs/Pet.md

@@ -4,10 +4,10 @@
 ## Properties
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-**id** | **kotlin.Long** |  |  [optional]
-**category** | [**Category**](Category.md) |  |  [optional]
 **name** | **kotlin.String** |  | 
 **photoUrls** | **kotlin.Array<kotlin.String>** |  | 
+**id** | **kotlin.Long** |  |  [optional]
+**category** | [**Category**](Category.md) |  |  [optional]
 **tags** | [**kotlin.Array<Tag>**](Tag.md) |  |  [optional]
 **status** | [**inline**](#StatusEnum) | pet status in the store |  [optional]
 

samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/models/Pet.kt

@@ -18,10 +18,10 @@ import com.squareup.moshi.Json
 import java.io.Serializable
 /**
  * A pet for sale in the pet store
- * @param id 
- * @param category 
  * @param name 
  * @param photoUrls 
+ * @param id 
+ * @param category 
  * @param tags 
  * @param status pet status in the store
  */