GH-3664: Re-enable JavaScript support via GraalVM (#3911)

* GH-3664: Re-enable JavaScript support via GraalVM

Fixes https://github.com/spring-projects/spring-integration/issues/3664

The JavaScript JSR223 engine has been removed from Java.

Migrate JavaScript support into GraalVM Polyglot API:
* Implement `PolyglotScriptExecutor` which can also support other GraalVM languages
* Change the `ScriptExecutorFactory` to use a `PolyglotScriptExecutor` when it encounters JavaScript
* Re-enable tests for JavaScript
* Add GraalVM Polyglot support into docs

* * Reinstate `@EnabledIfSystemProperty` for GraalVM JS system property

spring-integration-scripting/src/test/java/org/springframework/integration/scripting/config/jsr223/Jsr223HeaderEnricherTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

spring-integration-scripting/src/test/java/org/springframework/integration/scripting/config/jsr223/Jsr223InboundChannelAdapterTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2021 the original author or authors.
+ * Copyright 2013-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

spring-integration-scripting/src/test/java/org/springframework/integration/scripting/config/jsr223/Jsr223TransformerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.