Change assert_* to expect_* in tests

```
grep -Irl assert_ test/ | xargs sed -i \
    's/witness_assert/witness_do_not_replace/g';
grep -Irl assert_ test/ | xargs sed -i \
    's/malloc_mutex_assert_owner/malloc_mutex_do_not_replace_owner/g';

grep -Ir assert_ test/ | grep -o "[_a-zA-Z]*assert_[_a-zA-Z]*" | \
    grep -v "^assert_"; # confirm no output
grep -Irl assert_ test/ | xargs sed -i 's/assert_/expect_/g';

grep -Irl witness_do_not_replace test/ | xargs sed -i \
    's/witness_do_not_replace/witness_assert/g';
grep -Irl malloc_mutex_do_not_replace_owner test/ | xargs sed -i \
    's/malloc_mutex_do_not_replace_owner/malloc_mutex_assert_owner/g';
```

test/integration/cpp/basic.cpp

@@ -3,14 +3,14 @@
 
 TEST_BEGIN(test_basic) {
 	auto foo = new long(4);
-	assert_ptr_not_null(foo, "Unexpected new[] failure");
+	expect_ptr_not_null(foo, "Unexpected new[] failure");
 	delete foo;
 	// Test nullptr handling.
 	foo = nullptr;
 	delete foo;
 
 	auto bar = new long;
-	assert_ptr_not_null(bar, "Unexpected new failure");
+	expect_ptr_not_null(bar, "Unexpected new failure");
 	delete bar;
 	// Test nullptr handling.
 	bar = nullptr;