Scroll to the active cell when typing (in edit mode)

[brichet]

References

Follow up #14115

#14115 removed the scroll to the active cell on keydown event.
When the notebook is in edit mode and the active cell is not visible, using the keyboard should scroll to the active cell.

This PR restores this behavior, and removes some complexity included in the PR above.

Code changes

• scroll to the active cell on keydown event on the notebook in edit mode
• selectAbove() and selectBelow() notebook actions are not asynchronous anymore, which simplifies some tests.

This results in reverting asynchronous methods introduced in #15413

User-facing changes

Scroll to the active cell when typing, as previously.

Backwards-incompatible changes

None

cc @gabalafou @krassowski who worked on the related PR

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[brichet]

Test failures are not related

[fcollonval]

Thanks @brichet

[fcollonval]

Merging as the test will pass (the last commit is only adding a code comment)