fix: keydown events are prevented from bubbling in uui-table-cell

[iOvergaard]

Description

Fixes #437

If an input field is placed inside a table cell, you cannot type spaces in the field due to the fact that the surrounding uui-table-row is listening on "keydown" events and preventing them from bubbling.

This PR aims to make all events in the SelectableMixin act the same way so that we do not interfer with native events.

However, one caveat is that placing a uui-input inside a uui-table-row that is selectable will select that row when you click inside the field. There does not seem to be a way to prevent this, since we can only check on the composedPath() to detect which element you clicked on due to the generics of how the SelectableMixin works. Nothing bad happens when you do this, but you need to be aware of this caveat.

Types of changes

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

How to test?

1. There is a story set up to test this scenario in for uui-table-row and uui-table-cell

Checklist

• If my change requires a change to the documentation, I have updated the documentation in this pull request.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.