This test verifies that M62-M66 can be remapped through both python
and NGC, and that calling the original M-codes is supported in the
remap subroutine.

It also serves as an example of how to do this, since the M66 python
function needs to be a generator yielding `INTERP_EXECUTE_FINISH`.

Enabling M62-M66 to be remapped not only needs the codes added to
`interp_remap.cc`, but also the recursive call to the original
functions needs supporting code for mode 5 M-codes in
`interp_convert.cc` `convert_m()`, and for M62-M66 in
`rs274ngc_pre.cc`, `find_remappings()`.

The peculiar M66 needs special handling in the interpreter for
`input_flag`, and to ensure that its result (in param `#5399`) is
available within the remap, `Interp::synch()` runs `read_inputs()`.
