Fix backlight position of the manual row/column move plugins

[budnix]

Context

The PR fixes the backlight element position of the ManualColumnMove and ManualRowMove plugins.

Changes

Fix an issue where the backlight was misaligned when the mouse drag position began from the middle of the header.

Before

After

Fix an issue where the backlight was misaligned when the table was initialized without defining size (the window is a scrollable element). The bug existed only in the ManualRowMove plugin.

Before

After

and the last change is removing code for unsupported browsers (diff1, diff2)

How has this been tested?

I tested the changes locally and I covered the fixes 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/97
2. fixes https://github.com/handsontable/dev-handsontable/issues/99

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

[github-actions]

Launch the local version of documentation by running:

npm run docs:review f93cec3b40873c072b0fe492f7e58c0bf97c2525