Adds agnostic dropdown helper for QA tests

What does this MR do and why?

Continuing from !103215 (closed) but decoupled from a development branch.

This MR adds an agnostic dropdown component for the QA tests, so that the tests will continue to work when using our select2 implementation or the pajamas component.

It currently does not work completely as the interfaces between select2 and the pajamas component aren't yet compatible.

If select2 is detected in the section being searched, the component will defer to it.

Describe in detail what your merge request does and why.

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