Expand test coverage for AJAX

[aspark21]

Noting this down for reference, following on from some discussions in Moodle Dev chat. The current JMeter scripts do not call AJAX services.
The following rely heavily on AJAX:

• Moodle Dashboard
• Moodle Calendar
• Activity Completion

i.e. all of the key areas which have been found to be problematic at scale in the real world rather than through these tests.

Big value for Large Scale Moodle in improving this.

We're continuing to research this at UCL along with exploring the use of K6 on a pipeline.
Potential for a Moodle Partner to work with us on this. If we get anywhere, we'll be able to performance test our own site but will be very keen to contribute back for the benefit of all.