Support control over enabling plugin transformations between test and main source sets

[jeffdgr8]

There are scenarios where the Atomicfu Gradle plugin fails to transform test code to remove the Atomicfu runtime dependency, for example when atomics are used within a runBlocking coroutine lambda:

java.lang.IllegalStateException: Unsupported type of atomic receiver expression: GET_VAR 'val canceled: kotlinx.atomicfu.AtomicBoolean [val] declared in kotbase.BaseCoroutineTest.testCoroutineScopeListenerRemoved.' type=kotlinx.atomicfu.AtomicBoolean origin=null

But all the usages in the main source sets are able to be transformed successfully, so it's desirable to apply the plugin transformation to these published source sets, while just using the Atomicfu dependency directly in tests.

Alternatively, there are scenarios where atomics are only needed in tests and not in the main source sets. But applying the Atomicfu Gradle plugin to the module results in adding the Atomicfu runtime dependency to native targets in the main source sets, which is unnecessary.

It would be helpful to exclude certain source sets from the Gradle plugin's transformations as well as which source sets have the runtime dependency added. Also, if it could be determined which source sets don't actually require the runtime dependency (because atomics aren't used) and avoid adding it, this would be ideal.