run-tests: move test filtering into TestSuite.run()
Upcoming patches will move the execution of tests to separate processes.
To facilitate this, it makes sense to move logic out of Test.
Furthermore, test filtering is logically the domain of the test runner,
not the test itself.
This patch interrupts our mini series of factoring options into named
arguments because filtering consults many options and it is easier to
move this logic out of Test sooner so we don't have to introduce
arguments at all.
# The 9diff extdiff command generates diff(1) compatible output
# suitable for use with the plumber(4).
[extensions]
extdiff =
[extdiff]
9diff = /bin/mercurial/9diff -cm $parent $child $root