refactor[next]: move lift_mode itir test fixture into program_processor

[havogt]

Currently we have a mix of specifying the backend which already comes with a lift_mode default and separately the lift_mode fixture in some tests. The default was not overwritten in the roundtrip backend. Now we remove the separate lift_mode and add extra backends with the lift_mode set.

Note: we don't run double_roundtrip with temporaries and we don't use the lift_mode==SIMPLE_HEURISTIC in roundtrip, only USE_TEMPORARIES.

Longer term we should refactor all itir tests to use the ffront test infrastructure.

[edopao]

I think with this change we can also remove a couple of TODOs and temporary workarouds:

https://github.com/GridTools/gt4py/blob/main/src/gt4py/next/program_processors/codegens/gtfn/gtfn_module.py
TODO(tehrengruber): Remove lift_mode from call interface.

https://github.com/GridTools/gt4py/blob/main/src/gt4py/next/program_processors/runners/dace_iterator/workflow.py
TODO(tehrengruber): Remove lift_mode from call interface.

[havogt]

Thank you! Is this

gt4py/src/gt4py/next/program_processors/runners/dace_iterator/__init__.py

Line 253 in 2c06bc6

Currently only the `FORCE_INLINE` liftmode is supported and the value of `lift_mode` is ignored.

still true?

[edopao]

Thank you! Is this

gt4py/src/gt4py/next/program_processors/runners/dace_iterator/__init__.py

Line 253 in 2c06bc6

Currently only the `FORCE_INLINE` liftmode is supported and the value of `lift_mode` is ignored.

still true?

No, this comment is not true anymore. It can be removed.

[tehrengruber]

Just small things. Since LiftMode.SIMPLE_HEURISTIC is not tested anymore I would add either a comment to the heuristic or remove it.