tests: Add test for array slice assignment.

tests/basics/bytearray_slice_assign.py

+try:
+    bytearray()[:] = bytearray()
+except TypeError:
+    print("SKIP")
+    import sys
+    sys.exit()
+
+# test slices; only 2 argument version supported by Micro Python at the moment
+x = bytearray(range(10))
+
+# Assignment
+l = bytearray(x)
+l[1:3] = bytearray([10, 20])
+print(l)
+l = bytearray(x)
+l[1:3] = bytearray([10])
+print(l)
+l = bytearray(x)
+l[1:3] = bytearray()
+print(l)
+l = bytearray(x)
+#del l[1:3]
+print(l)
+
+l = bytearray(x)
+l[:3] = bytearray([10, 20])
+print(l)
+l = bytearray(x)
+l[:3] = bytearray()
+print(l)
+l = bytearray(x)
+#del l[:3]
+print(l)
+
+l = bytearray(x)
+l[:-3] = bytearray([10, 20])
+print(l)
+l = bytearray(x)
+l[:-3] = bytearray()
+print(l)
+l = bytearray(x)
+#del l[:-3]
+print(l)