[flang][hlfir] get rid of box when translating scalars to extented value (llvm#125059)

The code in `translateToExtendedValue(hlfir::Entity)` was not getting
rid of the fir.box for scalars because isSimplyContiguous() returned
false for them.

This created issues downstream because utilities using
fir::ExtendedValue were not implemented to work with intrinsic scalars
fir.box.

fir.box of intrinsic scalars are not very commonly used as hlfir::Entity
but they are allowed and should work where accepted.

Author: jeanPerier

flang/include/flang/Optimizer/Builder/HLFIRTools.h

@@ -125,7 +125,7 @@ class Entity : public mlir::Value {
   bool isSimplyContiguous() const {
     // If this can be described without a fir.box in FIR, this must
     // be contiguous.
-    if (!hlfir::isBoxAddressOrValueType(getFirBase().getType()))
+    if (!hlfir::isBoxAddressOrValueType(getFirBase().getType()) || isScalar())
       return true;
     // Otherwise, if this entity has a visible declaration in FIR,
     // or is the dereference of an allocatable or contiguous pointer