JAVA-12045 : move java concurrency ebook content code to common module (#12559)

* JAVA-12045 : move java concurrency ebook content code to common module

* JAVA-12045: addressed the review comments .. renamed package names and placed core-java-concurrency-simple module in pom.xml

* JAVA-12045: removed duplicate module after renaming java-simple-module to core-java-simple-module

core-java-modules/core-java-concurrency-simple/README.md

@@ -0,0 +1,18 @@
+### Mockito Articles that are also part of the e-book
+
+This module contains articles about Java Concurrency that are also part of an Ebook.
+
+## Relevant articles:
+
+- [Life Cycle of a Thread in Java](https://www.baeldung.com/java-thread-lifecycle)
+- [How to Start a Thread in Java](https://www.baeldung.com/java-start-thread)
+- [Thread's wait and notify() Methods in Java](https://www.baeldung.com/java-wait-notify)
+- [The Thread.join() Method in Java](https://www.baeldung.com/java-thread-join)
+- [Guide to the Synchronized Keyword in Java](https://www.baeldung.com/java-synchronized)
+- [Guide to the Volatile Keyword in Java](https://www.baeldung.com/java-volatile)
+- [A Guide to the Java ExecutorService](https://www.baeldung.com/java-executor-service-tutorial)
+- [Guide To CompletableFuture](https://www.baeldung.com/java-completablefuture)
+
+### NOTE:
+
+Since this is a module tied to an e-book, it should **not** be moved or used to store the code for any further article.