autotests: Use a shared library for the integration test framework
Ever since the effects were changed to static, each test of the integration tests includes all the effects. The result of this is that when doing a debug build each test is now 60MiB or more. With the amount of tests, this results in ~8 GiB of diskspace used just for KWin's binary output directory, which is rather excessive.
Since the tests all share a common framework library, we can change that library to a shared library and that way avoid linking all the effects into each test. The end result is that we now have a binary output directory that takes ~500MiB.
Most of this is shuffling around some link libraries in the integration test CMakeLists, however, I needed to export the Xwayland class as it is used by one of the tests but wasn't exported.