Investigate memory management issue with HttpRequest URLs in http_client.zig

Review and refactor how memory is managed for HttpRequest URLs, particularly in test scenarios where the deinit method tries to free global strings. Consider alternative approaches for test setups or memory management.

Reference:
```zig
// TODO: The request de-allocates the memory used by the url in the deinit method.
// Because of this, with this test, we have to dupe it or else it cant deinit a global string.
// Needing to do this is a sign that something is off here, but also newing up requests directly
// isn't really intended either. Either way, need to look into this further.
```