Investigate memoizing getRole

[straker]

We should do a performance audit on axe.commons.aria.getRole and see if we should memoize it. It's used heavily throughout the code and there are potential places where it can be called on the same element multiple times (and hundreds of times in some cases).

For example, in #3160 we need to look at the role of the parent table element of every row. On a site like https://web.archive.org/web/20190613132353/https://giveawaylisting.com/, that's hundreds to thousands of times the getRole function is called on the same element.

[LudwikJaniuk]

Looks interesting... following.
(I've been thinking if there are other things that could be memoized... perhaps involving links being repeated over a page?)