Fix editor incorrect width and height calculations

[budnix]

Context

The PR fixes a bug where the editor's max width and max height were incorrectly calculated. The bug appeared when the editor was opened on one of the overlays and the viewport was scrolled.

How has this been tested?

I tested the changes locally and covered the fix with new E2E tests.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Related issue(s):

1. fixes https://github.com/handsontable/dev-handsontable/issues/96

Affected project(s):

• handsontable

Checklist:

• I have reviewed the guidelines about Contributing to Handsontable and I confirm that my code follows the code style of this project.
• I have signed the Contributor License Agreement