[Sentry] Track loading of profile page

[mplorentz]

Create 3 Sentry transactions whenever we open a profile page.

1. One transaction for loading the profile metadata (name, display name, bio) that should complete whenever any of this data is displayed in the UI. Let's call it ProfileView.profileInfoLoad.
2. One transaction for loading the follow list (and relays) that finishes when they display in the UI. Let's call it ProfileView.followStatsLoad.
3. One transaction for the initial load of the user's notes. It should complete when we have loaded one full page of notes (30 notes). Let's call it ProfileView.feedLoad.

I'm making these criteria up out of thin air. If they are too complex to implement lets discuss alternatives.

Additionally, create a widget in our Sentry dashboard or three that we can use to see how long these transactions take on average. The goal here is to understand how long our users are typically waiting for the profile screen to load, and detect regressions.