Better tests for Java native client (#14132)

* add echo tests with java native client

* fix echo server

* fix github

* add npm install

* update samples

* add license header

* update smaples

* add test for array of string

* fix java native respone type casting

* better code format

* add license header

samples/client/echo_api/java/native/.openapi-generator/FILES

@@ -0,0 +1,36 @@
+.github/workflows/maven.yml
+.gitignore
+.travis.yml
+README.md
+api/openapi.yaml
+build.gradle
+build.sbt
+docs/Category.md
+docs/Pet.md
+docs/QueryApi.md
+docs/Tag.md
+docs/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.md
+git_push.sh
+gradle.properties
+gradle/wrapper/gradle-wrapper.jar
+gradle/wrapper/gradle-wrapper.properties
+gradlew
+gradlew.bat
+pom.xml
+settings.gradle
+src/main/AndroidManifest.xml
+src/main/java/org/openapitools/client/ApiClient.java
+src/main/java/org/openapitools/client/ApiException.java
+src/main/java/org/openapitools/client/ApiResponse.java
+src/main/java/org/openapitools/client/Configuration.java
+src/main/java/org/openapitools/client/JSON.java
+src/main/java/org/openapitools/client/Pair.java
+src/main/java/org/openapitools/client/RFC3339DateFormat.java
+src/main/java/org/openapitools/client/ServerConfiguration.java
+src/main/java/org/openapitools/client/ServerVariable.java
+src/main/java/org/openapitools/client/api/QueryApi.java
+src/main/java/org/openapitools/client/model/AbstractOpenApiSchema.java
+src/main/java/org/openapitools/client/model/Category.java
+src/main/java/org/openapitools/client/model/Pet.java
+src/main/java/org/openapitools/client/model/Tag.java
+src/main/java/org/openapitools/client/model/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.java

samples/client/echo_api/java/native/.openapi-generator/VERSION

@@ -0,0 +1 @@
+6.3.0-SNAPSHOT