Improve behavior of the viewport scroll after selection change

[budnix]

Context

The PR improves the viewport scroll's behavior after the selection change triggered by the mouse clicks. Additionally, the PR improves/fixes other things related to the viewport scroll behavior. The PR modularizes the viewport scrolling mechanism into a separate module that handles all scroll-related things.

The PR's changes:

Features

1. The viewport won't be scrolled after clicking the partially visible cell. The rule only applies in cases when the visible beginning of the cell is clicked (the cell is partially visible on the right edge of the table). When the end of the partially visible cell is clicked, the viewport is scrolled to the whole cell.

Bug fixes

1. Fixed a bug that causes the viewport to scroll in the wrong direction. It happens only after applying the selection for the first time (after table initialization).

Clicking on the beginning part of the partially visible cell (feature)

The same logic covers both axies, partially visible columns, and rows.

Before

After

Clicking on the end part of the partially visible cell (feature)

As before, so, and after the PR's changes, the behavior is the same. The viewport is scrolled to the beginning of the cell.

How has this been tested?

I tested the changes locally and I covered the feature with new tests.

Types of changes

• New feature or improvement (non-breaking change which adds functionality)

Related issue(s):

1. https://github.com/handsontable/dev-handsontable/issues/1689
2. https://github.com/handsontable/dev-handsontable/issues/1705

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 6d89addac04ccae23d9ed5412df931fa45d31237