[TESTBUG] Move gc stress tests from JFR directory tree to gc/stress

Most of tests under test/jdk/jdk/jfr/ are unit, functional or regression tests that execute quickly. However, there are some tests that are stress tests and take a long time. I have received a request to identify such tests and move them to another location (if possible), or remove them where applicable.

I am gathering the data first. Once I have a list of candidates we can discuss further.