tests: add filtercr.py helper for progress tests
The two tests that used filtercr.py already used a slightly different
version, which explains why test-convert-svn-move.t changed after
switching to using $TESTDIR/filtercr.py.
subrepo: re-backout
2245fcd0e160, remove test
7397a53219c9 re-removed the bad fix but not the test.
subrepo: re-backout
2245fcd0e160
This bug got introduced into default simultaneously with its backout,
so future merges didn't eradicate it.