Add trie walk test of partial leaf traversal

Recently, there was a fix for incorrectly raising a TraversedPartialPath
when traversing into a leaf, even if the suffix of the leaf did not
match the traversal path. See:
#114

This bug was actually found during a hypothesis run during a trie walk.
Although there are new unit tests making sure the leaf traversal works
properly, it seems worth adding the example explicitly as a kind of
backup test that the scenario works properly during a trie walk &
backfill.

tests/test_hexary_trie_walk.py

@@ -222,6 +222,16 @@ def test_trie_walk_backfilling_with_traverse_from(trie_keys, minimum_value_lengt
     index_nibbles=[],
     index_nibbles2=[],
 )
+@example(
+    # Catch bug where TraversedPartialPath is raised when traversing into a leaf,
+    #   even though the leaf suffix doesn't match the prefix that was being traversed to.
+    trie_keys=[b'\x00\x00\x00', b'\x10\x00\x00'],
+    minimum_value_length=26,
+    number_explorations=86,
+    trie_changes=[(1, None)],
+    index_nibbles=[],
+    index_nibbles2=[],
+)
 def test_trie_walk_root_change_with_traverse(
         trie_keys,
         minimum_value_length,