Tests package for DAMON is released under GPL v2

DAMON contains a number of tests based on the kselftest and kunit in its patchset itself. As it is preferred to contain only tests having short runtime in kernel tree, I organized time consuming tests in a package and used it in my company only. Tests could be used as a good document and essential for contributors. For the reason, I promised I will make it open source in the last kernel summit talk (https://linuxplumbersconf.org/event/7/contributions/659/).

Yesterday, I finally publicly released the package under GPL v2. Now you can use the package to understand the DAMON interface and test it on your machine by yourself.