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/unit/hash.c

@@ -131,7 +131,7 @@ hash_variant_verify_key(hash_variant_t variant, uint8_t *key) {
 	default: not_reached();
 	}
 
-	assert_u32_eq(computed, expected,
+	expect_u32_eq(computed, expected,
 	    "Hash mismatch for %s(): expected %#x but got %#x",
 	    hash_variant_string(variant), expected, computed);
 }