Fix navigation with actions & events

[paolodamico]

Closes #2393

[timgl]

I wonder if it's confusing to again separate actions and events, and if it wouldn't be better to just have them under one item? Will also reduce the number of items in the sidebar

[paolodamico]

You're right, that makes sense! I've removed the "Actions" item from the main navigation bar, but kept the logic to support custom scene handling stuff in case we want for instance add a specific insights item (e.g. funnels) directly to the menu.

Two small changes included in the PR too:

1. Fixes a small bug in which if you clicked the "Events" nav item and you were in a different tab, you were not taken to the main events tab.
2. Changed /events/events to /events/stats for more clarity.