WIP TRY_OPLINES: Move cop_line from COP to every OP

This reduces the need for almost all nextstate ops (99%), which is an
overall win in memory and speed for typical undense code, say for
maybe less than 4 ops per line.
Error reporting and warnings is also correct for multiline ops
without a cop (such as conditionals).

TODO:
* add dbstate ops on debugging, instead of just converting the
  nextstate ops.
* Check if the first cop of a new file is set correctly.
* Use the new op_line in line reporting, and do only walk back to the prev. cop
  for the file name.