Introduces a new test API, `includesModule`. The method returns whether
a particular module like "ajax" or "deprecated" is included in the current
jQuery build; it handles the slim build as well. The util was created so that
we don't treat presence of particular APIs to decide whether to run a test as
then if we accidentally remove an API, the tests would still not fail.
Closes gh-5071
Fixes gh-5069
Ref gh-5046
(partially cherry picked from commit fae5fee8b4)
Also, run such a suite in CI to make sure modules are working as expected
when used directly.
(partially cherry picked from 341c6d1b5a)
(partially cherry picked from 437f389a24)
Closes gh-4595
Ref gh-4550
Ref gh-4574