Use `assert.strictEqual`/`assert.true`/`assert.false`

When starting a cycle for a carousel, it only checks for a default interval, and not an interval defined on the slide element via data props. This adds a check in before creating the interval to move to the next slide.

Co-authored-by: XhmikosR <xhmikosr@gmail.com>

Firefox currently seems extremely fickle - with `pan-y` if fires pointercancel as soon as a touch strays even a pixel or so vertically.
While `touch-action: pan-y` would be ideal (allowing users to scroll the page even when their finger started the scroll on the carousel), this prevents a swipe that isn't perfectly/only horizontal to be recognised by Firefox.

- my fault, my original advice of using `touch-action: pan-x` is exactly the value we *don't* want to have the browser handle...

adds the ability to assign data-interval to an individual carousel-item

* Add carousel mouse listeners even if touch events enabled

- touch events are enabled not just on "mobile", just also on
touch-enabled desktop/laptop devices; additionally, it's possible to
pair a mouse with traditionally touch-only devices (e.g. Android
phones/tablets); currently, in these situations the carousel WON'T pause
even when using a mouse

* Restart cycle after touchend

as `mouseenter` is fired as part of the touch compatibility events, the
previous change results in carousels which cycle until the user
tapped/interacted with them. after that they stop cycling (as
`mouseleave` is not sent to the carousel after user scrolled/tapped
away).
this fix resets the cycling after `touchend` - essentially returning
to the previous behavior, where on touch the carousel essentially never
pauses, but now with the previous fix it at least pauses correctly for
mouse users on touch-enabled devices.
includes documentation for this new behavior.

Carousel - Add attributes from and to for Slid and Slide events

Fixes 2 bugs:

1. All keydowns were being prevented. Because of that the user wasn't able to navigate in the whole page using ARROW_UP/ARROW_DOWN.

2. Even when  is an input or textarea the keydowns were being prevented. Because of that the user wasn't able to type any text on these elements.

To ensure that we don't accidentally use any of the aliases.
This should prevent any future regressions from #12761.
Also updates the test suite since it now can't use these aliases either.

[Fixes #15953] Implement `assert.expect` in each unit test

Refs #15893

[skip validator]

[skip validator]

[skip validator]