Add small test that :command processing works.
Remove :c (old test code).
Add test.physkeys() (send a string of keys without coroutine handling).
Add test.assertAt() as a convenience to check the row/col in one go.  This
and assertEq() now use a common helper which allows changing the level to
attribute the error to.
Add a partial (failing) search test.
Add testcases for * and #.  But still failing on '2n'.
Add testcase for using search as an acdtion motion.
Move n, N, *, # to vi_motion.  Fixes '2n' etc.