kotlinx.atomicfu compiler plugin for JS_IR backend (#4581)

* kotlinx.atomicfu compiler plugin for JS_IR

Support transformations of atomic operations introduced by the kotlinx.atomicfu library for the JS_IR backend. Compiler plugin is applied externally by the kotlinx.atomicfu gradle plugin.

* Apply compiler plugin for JS platform only

* New plugin test structure

* testGroupOutputDirPrefix changed

libraries/configureGradleTools.gradle

@@ -3,6 +3,7 @@ def pluginProjects = [
         project(':kotlin-allopen'),
         project(':kotlin-noarg'),
         project(':kotlin-serialization'),
+        project(':atomicfu'),
         project(':kotlin-lombok')
 ]
 configure(pluginProjects) { project ->