async function name was changed to waitForAsync but it was left in testing-utility-api file. PR Close #38548
The last commit change `async` to `waitForAsync`. This commit update all usages in the code and also update aio doc. PR Close #37583
This commit breaks up the testing document into nine total documents, with each document focusing on an existing section of the current testing documentation. There are no content changes. PR Close #37957