The bandwidth track should display the average transfer speed in the tooltip when a range is selected

[mstange]

Profile: https://share.firefox.dev/3ZdX7jt

Select a range. I would like to see the following information in the tooltip of the bandwidth track:

• What's the average transfer speed in the selected range?
• Optional: What's the total number of read / write calls in the selected range?

┆Issue is synchronized with this Jira Task