Support for nested test suites

[ekharchenko-avito]

• merged William Petit changes to support suite-in-suite embedding
• added suite Properties fulfillment from attributes (like it already was for testcase)
• added test for that

[ekharchenko-avito]

Would it make any sense to flatten the structure into something like this:

That don't make sense for my use case. That will give /untitled/tests.SampleTest.SampleTest::testB in an example PHPUnit file which is a mess of original command line tests selector, class name, and test method name. Don't really want to parse-out those parts from the flattened name in production code.

[joshdk]

Apologies for the delay @ekharchenko-avito. Thank you so much for your contribution! 🎉