Fix `ift.Field.vdot` breaking with np.uint32 and other integer types

Hi Martin,

I just stumbled over ducc0.misc.vdot not multiplying doubles and integers, which is required in the PoissonianEnergy. It seems Philipp Arras did so, too, a while ago, but unfortunately his mitigation was incomplete, as it did only catch np.int64s.

Is there a double*integer vdot in ducc0 that we could call instead of the conversion?

While at it: I noticed ift.PoissonianEnergy enforces integer-typed data fields (sensible for Poisson counts), but then passes them directly to vdot, triggering an int->double conversion in each application. Should we cast the data field to double in the initialization of PoissonianEnergy after the integer check to avoid this?

Cheers, Lukas

src/ducc_dispatch.py

@@ -49,9 +49,9 @@ try:
 
 
     def vdot(a, b):
-        if isinstance(a, np.ndarray) and a.dtype == np.int64:
+        if isinstance(a, np.ndarray) and np.issubdtype(a.dtype, np.integer):
             a = a.astype(np.float64)
-        if isinstance(b, np.ndarray) and b.dtype == np.int64:
+        if isinstance(b, np.ndarray) and np.issubdtype(b.dtype, np.integer):
             b = b.astype(np.float64)
         return ducc0.misc.vdot(a, b)