swap/io metric incorrectly named

The `swap/io` metric [is documented](https://cloud.google.com/monitoring/api/metrics_opsagent#agent-swap) as "Total count of swap I/O operations by direction.", and labelled "Swap I/O operations" in the monitoring dashboard.

However, this seems to be [a rename](https://github.com/GoogleCloudPlatform/ops-agent/blob/e5cc70b94baaa241f14d49e2059d275e1e4d9264/apps/hostmetrics.go#L227) of the OpenTelemetry [`system.paging.operations` metric](https://opentelemetry.io/docs/specs/semconv/system/system-metrics/#metric-systempagingoperations), [documented as](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/receiver/hostmetricsreceiver/internal/scraper/pagingscraper/documentation.md#systempagingoperations) "The number of paging operations.".

As this is related to all paging operations not just those related to swap, and not necessarily related to I/O, this metric seems to be incorrectly labelled and named which caused us some confusion when we were tracing swap behavior but not seeing any actual swap operations.