run-tests: add more scheduling weight hints

The scheduler would like to order test execution by expected run-time,
but doesn't know much about how long a test will run. It thus uses
test size as a proxy for run-time. By tweaking these weights we can
keep CPUs more evenly busy and thus finish sooner.

In particular, this change pushes the three currently longest-running
tests closer to the beginning:

test-largefiles-update.t
test-run-tests.t
test-gendoc.t

As the largefiles test is currently the long pole of the test suite
with higher -j factors, the sooner it's started, the sooner the tests
can end.

We also up the weight on some shorter but long-running tests that
could have previously delayed completion with low -j factors by
running very close to the end.

tests/run-tests.py

@@ -1744,8 +1744,15 b' class TestRunner(object):'
         else:
             # keywords for slow tests
             slow = {b'svn': 10,
-                    b'gendoc': 10,
-                    b'check-code-hg': 100,
+                    b'cvs': 10,
+                    b'hghave': 10,
+                    b'largefiles-update': 10,
+                    b'run-tests': 10,
+                    b'corruption': 10,
+                    b'race': 10,
+                    b'i18n': 10,
+                    b'check': 100,
+                    b'gendoc': 100,
                     b'contrib-perf': 200,
                    }
             def sortkey(f):