test: make it easier to run tests for subsystems

You can now run suites for subsystem using shorthand, e.g., http.
Switch to black-list of default test folders from white-list.
Tests run by 'make test', 'make coverage', etc., now configurable.
Stop running known_issues suite when collecting test coverage.

PR-URL: https://github.com/nodejs/node/pull/15450


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>