Make organisation stats retrieval async

[suecarmol]

Description

• Changed the stats shown in organisations asynchronous
• Removed synchronous code in organisations/views.py
• Removed common templates that are no longer used.

Rationale

Some pages were timing out or taking too long to load. This helps solve this issue.

Phabricator Ticket

T351860

How Has This Been Tested?

Tested manually by loading different organisations and seeing if they time out or not.

Screenshots of your changes (if appropriate):

Types of changes

What types of changes does your code introduce? Add an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

[katydidnot]

Thanks for your work on this! It's looking good. Also, was a great opportunity to get familiar with WikiLinks! 🥳

I just had a few questions, some minor nitpicks, and one dev console exception.

[jsnshrmn]

This looks good and works well in local testing. Thanks!