[BUG] On sites with monetized AND non-monetized pages, non-monetized pages count for monetized time about akita

[sharon-wang]

This issue cannot be closed until #17 is complete. It's possible for a site to have monetization enabled, but then have its payment pointer removed, however the time spent on the site would still be added to its total monetized time spent, which is not correct. If we are checking anytime the payment pointer is changed, then we will be able to differentiate between monetized time spent and non-monetized time spent in this situation.

[sharon-wang]

We can update our data storage to store monetized time spent per payment pointer per origin. Each origin will also hold the total monetized time spent at the origin in addition to the total time spent at the origin.

We currently calculate totalMonetizedTimeSpent and store it into originStats. We will need to modify how this time is being tracked so that we instead track it per payment pointer, but we still store the total time in originStats.

We may need to make changes to the extension popup UI, since we only display the total time spent per origin, but we may want to indicate the total monetized time spent per origin too.

[sharon-wang]

Monetized time spent will still be stored at the origin level, not at the payment pointer level, to avoid complicating the data.