WIP: Add lower function

[ZzEeKkAa]

Numba added lower as an argument to some functions.

Few more changes required, since this part of code does not work anymore (numba_dpex/core/passes/lowerer.py:1423):

                self.cpu_lower.context.lower_extensions[
                    parfor.Parfor
                ] = _lower_parfor_parallel

AttributeError: Failed in dpex_offload_nopython mode pipeline (step: Custom Lowerer with auto-offload support)
E                'CPUContext' object has no attribute 'lower_extensions'

#1000

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[diptorupd]

Superseded by #1030