Components: Improve BoxControl tests (#45968)

* Fix no-node-access violation

* Get rid of getInput() and improve input query

* Get rid of getSelect() and improve combobox query

* Get rid of getReset() and improve reset button query

* Get rid of setupUser() and inline it

* Add spaces to improve readability

* Improve test name

* Inline all constants that are used just once

* Use toHaveLength to improve assertion

* Revert unwanted change

* Improve precision of existing queries

* Use the same mock for setState(), improve assertions