The following metrics are now always recorded and available via the new
uv_metrics_info() API.
* loop_count: Number of event loop iterations.
* events: Total number of events processed by the event handler.
* events_waiting: Total number of events waiting in the event queue when
the event provider request was made.
Benchmarking has shown no noticeable impact recording these metrics.
PR-URL: https://github.com/libuv/libuv/pull/3749
e141586053