Make the answer select elements' labels for matching question types more meaningful

This was split off from MDL-71301 to improve the labelling of the answer select elements for matching type questions.

From the original issue's description:

Match question:

Each drop-down list has an off-screen label named "Answer 1", "Answer 2", and so on. It would be more relevant if the label contained a meaningful element of the question. Here are some functional benefits of this practice:

a) If the answer field is linked to a meaningful label, this provides additional security to enter the “right thing” in the “right place”.

b) JAWS AND NVDA provide a function that lists all of the form controls on a page. The drop-down lists will be easier to identify.

c) In JAWS and NVDA, activating a form control starts Form view. In this mode, the fields and their labels are read, but not the regular textual elements. There is therefore a risk of missing the names of theorists as they are currently coded, unless you systematically order an exit from Form mode.

However, we got the following recommendation from the company doing accessibility audits for Moodle LMS:

“Answer 1”, “Answer 2” et cetera is not descriptive enough, and something like “Select an answer” or “Select an answer to this question” would be an improvement. I feel adding additional and possibly duplicated content will cause more confusion than leaving it as it currently is.