Modified how fill() works, it now also accepts non variables.

This changes makes it possible that the `fill()` function accepts variables.
However, this particular commit only allows variables that where passed as arguments, at least in some sense, see the discussion of the issue.

This is a first step to address issue [spcl#1389](spcl#1389).

dace/frontend/python/replacements.py

@@ -4234,6 +4234,10 @@ def _ndarray_copy(pv: ProgramVisitor, sdfg: SDFG, state: SDFGState, arr: str) ->
 @oprepo.replaces_method('View', 'fill')
 def _ndarray_fill(pv: ProgramVisitor, sdfg: SDFG, state: SDFGState, arr: str, value: Number) -> str:
     if not isinstance(value, (Number, np.bool_)):
+        pass        # Litteral numbers passed as arguments
+    elif isinstance(value, str) and isinstance(sdfg.arrays.get(value, None), data.Scalar):
+        pass        # Scalars inside the sdfg (is this safe?)
+    else:
         raise mem_parser.DaceSyntaxError(pv, None, "Fill value {f} must be a number!".format(f=value))
     return _elementwise(pv, sdfg, state, "lambda x: {}".format(value), arr, arr)