Add a way to check library version at runtime

[PierfrancescoSoffritti]

We are in the process of enabling coroutine debugging on Android Studio. In order to make it work we had to fix some performance issues on the coroutine debugger.

As these improvements are available only to devs using kotlinx-coroutine-core version 1.6+, we decided to disable the debugger for devs using older versions of the lib, as the debugger is not usable there.

In order to do this we have two options:

1. Check version of the lib at build time. This will require adding a dependency to the build system, which we want to avoid because it's not reliable and a common source of bugs.
2. Check version of the lib at runtime. This will require adding some versioning info to the lib's jar. In Androidx libs we add a META-INF/some_file.version file to the jar, containing the version number. Something similar could be done for coroutines, to allow our agent to check it at runtime.