Implement Source DocumentationProvider, spring-mvc decommission (#11531)

* - Upgrade swagger-ui to 4.4.1
- Bring homeController.mustache up-to-date
- Main class is now OpenApiGeneratorApplication
- Introduce SpringBootTest.mustache
- Remove option swaggerDocketConfig/openapiDocketConfig in favor of documentationProvider.

* Generate Samples

* Restore generator-online classes
Fix spring-mvc builds

* Generate Samples

* Do not generate SpringFoxConfiguration.java when reactive ist set.

* Fix generation of SpringFoxConfiguration

* Generate Documentation

* Reactive support: add dependency management for springdoc-openapi-webflux-ui

* Generate Samples

* Change SpringBootApplication to OpenApiGeneratorApplication

* Generate Samples

* Implement SwaggerUIFeatures in SpringCodegen

* Generate Samples

* Add useSwaggerUI: true to some test configs

* Generate Samples

* Update Documentation

* Update Documentation

* Update README.mustache

* Generate Samples

* useSwaggerUI is true by default

* Generate Samples

* Update Documentation

* Add deprecation warnings to cli opts; Log a deprecation warning

* Update Documentation

* Generate Samples

* Remove spring-mvc library

* Remove spring-mvc from project and CI configs

* Check whether the selected documentation provider requires us to boostrap swagger-ui.

* Generate Samples

* Generate samples

* Generate samples

* Generate samples

samples/server/petstore/springboot-spring-pageable-delegatePattern/.openapi-generator/FILES

@@ -1,6 +1,6 @@
 README.md
 pom.xml
-src/main/java/org/openapitools/OpenAPI2SpringBoot.java
+src/main/java/org/openapitools/OpenApiGeneratorApplication.java
 src/main/java/org/openapitools/RFC3339DateFormat.java
 src/main/java/org/openapitools/api/AnotherFakeApi.java
 src/main/java/org/openapitools/api/AnotherFakeApiController.java
@@ -22,6 +22,7 @@ src/main/java/org/openapitools/api/UserApi.java
 src/main/java/org/openapitools/api/UserApiController.java
 src/main/java/org/openapitools/api/UserApiDelegate.java
 src/main/java/org/openapitools/configuration/HomeController.java
+src/main/java/org/openapitools/configuration/SpringFoxConfiguration.java
 src/main/java/org/openapitools/model/AdditionalPropertiesAnyType.java
 src/main/java/org/openapitools/model/AdditionalPropertiesArray.java
 src/main/java/org/openapitools/model/AdditionalPropertiesBoolean.java
@@ -70,3 +71,5 @@ src/main/java/org/openapitools/model/User.java
 src/main/java/org/openapitools/model/XmlItem.java
 src/main/resources/application.properties
 src/main/resources/openapi.yaml
+src/main/resources/static/swagger-ui.html
+src/test/java/org/openapitools/OpenApiGeneratorApplicationTests.java