Port Structured.scala to Structured.java

[jabrena]

• https://github.com/xebia-functional/Unwrapped/blob/main/unwrapped/src/main/scala/unwrapped/Structured.scala
• https://github.com/xebia-functional/Unwrapped/blob/main/unwrapped/src/test/scala/unwrapped/StructuredTests.scala

[jabrena]

• https://github.com/ishwi/Chuu/blob/master/src/main/java/core/util/VirtualParallel.java
• https://github.com/forax/loom-fiber/blob/master/src/main/java/fr/umlv/loom/example/_15_adhoc_scope.java
• https://github.com/codetojoy/easter_eggs_for_java_loom/blob/main/egg__11_sc_utility/src/main/java/net/codetojoy/CustomScope.java
• https://github.com/SvenWoltmann/structured-concurrency/blob/main/src/main/java/eu/happycoders/structuredconcurrency/demo3_suppliers/BestResultScope.java
• https://github.com/daqingllm/Java21-for-backend-developers-code/blob/main/src/main/java/chapter2/MyScope.java