* tests: IE<11 does not understand const/let

* tests: specify all required initEvent arguments for (IE)

Otherwise we get: TypeError: Argument not optional

* tests: add profiles to emulate legacy IE versions in IE11

I can confirm that only IE10 profile is working.

Sample commandline:

npm run test-nolint -- --browsers IE,IE10

* tests: consider that style.zIndex is Number type in IE

* tests: set container height explicitly to fix 6 tests failing in IE

in IE when container.style.height is not set, container.clientWidth is always 0, despite container.style.width value.

* tests: fix #preventDefault in IE

Event properties is not preserved across different listeners calls in IE,
so we have to make all checks in the same listener.

Also: control case added.

Note: previously here used to be different implementation that was also reliable,
as it relied on return value of https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/dispatchEvent

```
		function dispatchClick(el) { // return: cancelled
			if (document.createEvent) {
				var e = document.createEvent('MouseEvents');
				e.initMouseEvent('click', true, true, window,
					0, 0, 0, 0, 0, false, false, false, false, 0, null);
				return el.dispatchEvent(e);
			} else if (el.fireEvent) { // IE<11
				return el.fireEvent('onclick');
			}
		}

		it('prevents the default action of event', function () {
			expect(dispatchClick(el)).to.be.ok(); // control case

			L.DomEvent.on(el, 'click', L.DomEvent.preventDefault);

			expect(dispatchClick(el)).to.not.be.ok();
		});
```

* tests: skip crossOrigin-related tests in IE<11

https://caniuse.com/mdn-html_elements_img_crossorigin