Some of our existing tests can't be run with any other test concurrently (e.g. b/c they consume all available memory or stress system in some other way). Currently, such tests use `exclusiveAccess.dirs`, but it doesn't fully provide the desirable behavior (as they still can be executed w/ other non-exclusiveAccess tests), or are placed in a separate directory and executed w/ -concurrency=1 (this approach has obvious drawbacks related to extra overhead and makes test execution somewhat more complicated).

see https://mail.openjdk.java.net/pipermail/jtreg-dev/2019-March/000761.html for the previous discussion.