Load the activities tab of submission and project on demand (#3330)

The activities tab can have a lot of activities as it’s unpaginated 
and also has an N+1 query to fetch the related objects.

This PR loads the data only after the tab is clicked.

I makes use of the htmx and alpine to observe the window-hash change. 

Notes:
- The communication tab with it's markdown editor, requires some custom
initialization logic, which breaks with the htmx loaded content. So it'
not included in this PR.
- On a submission with 5 activities the number of SQL queries reduced
from 168 to 148.

Related #3328