Ensure that the bottom/right cell borders are visible in the viewport after scrolling from the absolute top/absolute left table position.

[jansiegel]

Context

This PR:

• Adds a 1px row/column header border compensation to the scroll values when scrolling from the absolute top/absolute left positions of the table using the API.
• Modifies the test cases to match the new scroll values. I went through all of them to make sure they were correct. In some cases, it's up for debate (for example, in the case explained in the first bullet point, the offset cols/rows are now loaded differently), but I don't think this should negatively impact the scrolling in general.
• Adds a new test case to ensure the borders are visible after scrolling.

How has this been tested?

Tested manually + added a new test case.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature or improvement (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Additional language file or change to the existing one (translations)

Related issue(s):

1. handsontable/dev-handsontable#1772

Affected project(s):

• handsontable
• @handsontable/angular
• @handsontable/react
• @handsontable/vue
• @handsontable/vue3

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
• My change requires a change to the documentation.

[github-actions]

Launch the local version of documentation by running:

npm run docs:review 052fd0094eb6e1bba40f80bb364924c718d6155c