Use `withChartViewport` inside the network chart component

Currently we don't use `withChartViewport` and handle the viewport related logic in in there. But Markus pointed out [here](https://github.com/firefox-devtools/profiler/pull/5548#issuecomment-3179327966) that because of this network chart doesn't support pinch-zoom and panning. We should make this component use `withChartViewport` so it can support these, and we can simplify the mouseMove event handler by removing `getBoundingClientRect` and a bunch of margin related constants.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-924)