[next]: GTIR cleanup tasks

[tehrengruber]

Let's track all cleanup tasks for GTIR in this branch. Please reference this issue in all the TODOs you write in the codebase, e.g. # FIXME[#1582](<github_name>): ... .

Tasks:

• Disable CI for gtir branch again (github + CSCS CI) ci[next]: Enable Github CI on GTIR branch #1581
• Remove left-overs of Fencil: the Node itself, temporar constructs like FencilToProgram etc.
• Use new TraceShift API in domain inference
• Remove GTFN dependency of column_axis as soon as the scan is operating on fields.
• Remove __gt_itir__ and use __gt_gtir__ or fix otherwise (e.g. removing the protocol altogether).

Misc:

• Add checks to GTIR/ITIR type inference that checks:
  if_(cond_: bool, true_v: scalar, false_v: scalar)
cond(cond_: bool, true_v: Field | tuple, false_v: Field | tuple) EDIT: obsolete we removed cond