Integration tests

This is a supplementary project that provides integration tests.

The tests are the following:

mavenTest depends on the published artifacts and tests artifacts binary content for absence of atomicfu in the classpath.
jvmCoreTest miscellaneous tests that check the behaviour of kotlinx-coroutines-core dependency in a smoke manner.
coreAgentTest checks that kotlinx-coroutines-core can be run as a Java agent.
debugAgentTest checks that the coroutine debugger can be run as a Java agent.
debugDynamicAgentTest checks that kotlinx-coroutines-debug agent can self-attach dynamically to JVM as a standalone dependency.
smokeTest builds the multiplatform test project that depends on coroutines.

The integration-testing project is expected to be in a subdirectory of the main kotlinx.coroutines project.

To run all the available tests: ./gradlew publishToMavenLocal + cd integration-testing + ./gradlew check.