Complete module tests

Problem/Motivation

Within https://www.drupal.org/project/views_autocomplete_filters/issues/3428016 📌 Add tests Fixed tests were added to module.
But only Functional Javascript tests were implemented ... as it's the "main area" of this module solutions.

Still missing Kernel and Functional tests and some more scenarios/use cases.

Steps to reproduce

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Proposed resolution

- Cover "Allow Contextual filters to apply to this filter" option,
@see the guilty issue https://www.drupal.org/project/views_autocomplete_filters/issues/3259438 ✨ Not working with contextual filters Fixed that intoduced it.
- Functional - TBD - Is it really needed? What are the benefits? Plan (what to cover), if needed.
- Kernel - TBD - Is it really needed? What are the benefits? Plan (what to cover), if needed.

Remaining tasks

- First: Plan
- Second: create child issue for every "issue/task"
- Provide solutions for each one.