Fix ->repeat with iterator, make t/repeat.t pass (formerly t/todo-repeat.t)

Fix ->repeat with iterator, make t/repeat.t pass (formerly t/todo-repeat.t)

The change to ->repeat method in HTML::Zoom::FilterBuilder assumes
that when it is passed code reference, it is meant to be used as
iterator (i.e. turned into stream using 'stream_from_code').

This made t/todo-repeat.t pass.  This test got renamed to t/repeat.t
now that it no longer needs to be skipped.  Instead of just testing
that there are no errors, it checks that ->repeat(sub { ... }) works
correctly.  Added test for equivalent ->repeat([ ... ]).

The t/flush.t test no longer needs workaround for ->repeat() (and it
doesn't work with workaround now, hmmm...).