Add administrative REST API endpoints to RangeHTTPServer allowing tests to:
- Configure HTTP return codes for specific paths:
* PUT /admin/status-rules to set rules
* Support time-based expiry with "during" parameter
* Support count-based expiry with "repeat" parameter
* DELETE /admin/status-rules/<path> to remove rules
- Track failure statistics:
* PUT /admin/failure-counts/start to begin monitoring
* GET /admin/failure-counts/<path> to get current count
Useful for testing HTTP retry mechanisms, error handling and failure
recovery behaviors.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8128>
78cf4706d9