tests/stress: Add test to create a dict beyond "maximum" rehash size.

There is a finite list of ascending primes used for the size of a hash
table, and this test tests that the code can handle a dict larger than the
maximum value in that list of primes.  Adding this tests gets py/map.c to
100% coverage.

tests/stress/dict_create_max.py

@@ -0,0 +1,13 @@
+# The aim with this test is to hit the maximum resize/rehash size of a dict,
+# where there are no more primes in the table of growing allocation sizes.
+# This value is 54907 items.
+
+d = {}
+try:
+    for i in range(54908):
+        d[i] = i
+except MemoryError:
+    pass
+
+# Just check the dict still has the first value
+print(d[0])