Fixes #1759

Description

The culprit of the Internal Error was PHP's uasort, which we were using to sort activity leaving indices in place. Leaving indices in places potentially makes the array incompatible of being serialized as a JSON array. We don't care about the indices, so they can be tossed using usort instead.

Additionally:

• Now display date and time and moved it to the far right (because that seemed more intuitive to me)
• Found something meaningful to put in the "Fields" column as it seemed to be broken,
• Fixed the partially broken sorting (it was comparing user objects (which are never the same) instead of user names)
• Added a loading indicator, because loading all activity can take a while

Almost removed the sorting by username before time functionality, but...maybe it's useful and I made enough changes 🤷.
There are no indications that the list is not truly chronological and a truly chronological sort seems more compatible with real-time collaboration.

Yup, I see now that the original code uses tabs and I used spaces.

Screenshots

Checklist

• I have labeled my PR with: bug, feature, engineering, security fix or testing
• I have performed a self-review of my own code
• I have reviewed the title & description of this PR which I will use as the squashed PR commit message
• I have commented my code, particularly in hard-to-understand areas
  I have added tests that prove my fix is effective or that my feature works
• I have enabled auto-merge (optional)

Testing

Testers, use the following instructions against our staging environment. Post your findings as a comment and include any meaningful screenshots, etc.

1. View project activity
2. Make sure the column content seems reasonable
3. Observe no errors