Changes:
* add `tests/lib/vendor/**/*` to `.eslintignore`
* move `qunit-composite` to `tests/lib` so that we can modify it
* move `qunit-assert-classes` to `tests/lib` so that we can modify it
* move `qunit-assert-close` to `tests/lib` so that we can modify it
* replace `assert.push` with `assert.pushResult`
* remove usage of `QUnit.extend`
Closes gh-2157
This helps fix issues that make tooltip tests sometimes fail when run against
jQuery 3.2 or newer due to timing differences.
Details:
* Add the `moduleAfterEach` function ensuring no timers are running.
* Attach this function via `common.testWidget`.
* Attach this function to most test suites.
* Add a tooltip test helper cleaning up leftover timers.
* Rename legacy `setup`/`teardown` hooks to `beforeEach`/`afterEach`.
Closes gh-1920
