run-test.py: greatly increase the priority of 'check-code' tests
As check-code is actually quite long to run for its file size, this prevent them
to be scheduled too late during the test run.
This reduces my typical test run from 107 seconds to 90 seconds
$ hg init
$ echo 123 > a
$ hg add a
$ hg commit -m "first" a
$ mkdir sub
$ echo 321 > sub/b
$ hg add sub/b
$ hg commit -m "second" sub/b
$ cat sub/b
321
$ hg co 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ cat sub/b 2>/dev/null || echo "sub/b not present"
sub/b not present
$ test -d sub || echo "sub not present"
sub not present