Add np.ndarray.ptp() support.

As title, just wiring.

Fixes numba#6257

numba/np/arraymath.py

@@ -1106,6 +1106,7 @@ def impl(val):
     return impl
 
 
+@overload_method(types.Array, 'ptp')
 @overload(np.ptp)
 def np_ptp(a):
 

numba/tests/test_array_reductions.py

@@ -128,6 +128,9 @@ def array_nanpercentile_global(arr, q):
 def array_ptp_global(a):
     return np.ptp(a)
 
+def array_ptp(a):
+    return a.ptp()
+
 def array_quantile_global(arr, q):
     return np.quantile(arr, q)
 
@@ -797,6 +800,17 @@ def a_variations():
         for a in a_variations():
             check(a)
 
+    def test_ptp_method(self):
+        # checks wiring of np.ndarray.ptp() only, `np.ptp` test above checks
+        # the actual alg
+        pyfunc = array_ptp
+        cfunc = jit(nopython=True)(pyfunc)
+
+        a = np.arange(10)
+        expected = pyfunc(a)
+        got = cfunc(a)
+        self.assertPreciseEqual(expected, got)
+
     def test_ptp_complex(self):
         pyfunc = array_ptp_global
         cfunc = jit(nopython=True)(pyfunc)