bug[next]: ConstantFolding after create_global_tmps (#1756)

Do `ConstantFolding` within `domain_union` to avoid  nested minima and maxima by `create_global_tmps`

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Co-authored-by: Till Ehrengruber <[email protected]>

src/gt4py/next/iterator/ir_utils/domain_utils.py

@@ -16,6 +16,7 @@
 from gt4py.next.iterator import ir as itir
 from gt4py.next.iterator.ir_utils import ir_makers as im
 from gt4py.next.iterator.transforms import trace_shifts
+from gt4py.next.iterator.transforms.constant_folding import ConstantFolding
 
 
 def _max_domain_sizes_by_location_type(offset_provider: Mapping[str, Any]) -> dict[str, int]:
@@ -168,6 +169,8 @@ def domain_union(*domains: SymbolicDomain) -> SymbolicDomain:
             lambda current_expr, el_expr: im.call("maximum")(current_expr, el_expr),
             [domain.ranges[dim].stop for domain in domains],
         )
+        # constant fold expression to keep the tree small
+        start, stop = ConstantFolding.apply(start), ConstantFolding.apply(stop)  # type: ignore[assignment]  # always an itir.Expr
         new_domain_ranges[dim] = SymbolicRange(start, stop)
 
     return SymbolicDomain(domains[0].grid_type, new_domain_ranges)