improve whole-page performance by scoping events handlers

[tinovyatkin]

Description

This is a further improvement over #703 and #696. We have mousedown event handler in capture mode for document.documentElement, while inside of it immediately returning if element is not part of outerContainer. So, that logically means we should initially set our target element properly.

Similar logic was applied to keydown and mouseover handlers.

Also fixed here invalid arguments and target for removeEventListener, introduces by #703 (sorry 🤷🏼‍♂️)

While we were here, reimplemented #710 in a little bit more performant way and with support for LTR/RLT directions.

Noticing, that isIE11 util had being used only at mouse down handler and that result of this function call are always constant for the same browser, replacing it with a constant and using feature detection instead of userAgent sniffing.

As a result of the above refactorings removed two obsolete helpers from utils.

Screenshots (if appropriate)

Types of changes

• Chore (tooling change or documentation change)
• Refactor (non-breaking change which maintains existing functionality)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.