refactor(filter): use PolarInput

[dopenguin]

Summary

Replaces layout-conditional checkbox/radio components (KernBlockButtonCheckbox, KernCheckbox, KernBlockButtonRadioGroup, KernRadioGroup) in filter with the unified PolarInput component (as proposed in #734).
Simplifies category state from Record<string, boolean> to string[] and introduces a reactive getter/setter-based selection model on categories for direct v-model binding and to get rid of getCategoryStatus and setCategoryStatus.

Also added some small changes to PolarInput and PolarInputGroup.

Instructions for local reproduction and review

1. npm run snowbox
2. Open filter
3. Verify category checkboxes can be toggled individually and via "Alle an-/abwählen"
4. Verify the 1xx multi-value category entry correctly selects/deselects with its individual values (100, 101, 102)
5. Verify time filter works
6. Verify the date range picker scrolls into view when "Zeitraum wählen" is selected and selection works

Additional information

I intend to update the implementation in src/plugins/filter/stores/category.ts (a) and src/plugins/filter/stores/time.ts (#811) as well.
For (a): Currently, if a user switches between two layers, the filter state of the the previous layer is reset. This is odd from a usability perspective. If you agree, I'll change this in a separate PR so that the state stays even if the layer switches.

Tickets

Resolves #779

[github-actions]

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[oeninghe-dataport]

Without looking into the code, it's stated in #779:

The standard layout's block-button styling is applied via CSS (e.g. a class on the group or scoped styles)

However, the standard layout is not intact anymore but looks like the nineRegions layout.

Before:

After:

Please update your PR such that the styling before is still working.

[dopenguin]

Without looking into the code, it's stated in #779:

The standard layout's block-button styling is applied via CSS (e.g. a class on the group or scoped styles)

However, the standard layout is not intact anymore but looks like the nineRegions layout.

Before:

After:

Please update your PR such that the styling before is still working.

After consulting with UX, I've adjusted the issue to scrap the block-button styling as the radios and checkboxes should not behave the same visually as one would not properly discern the possibility to select multiple elements with the checkboxes or is confused as one would only be able to select one element with the radio buttons.
We can revisit this approach later again if needed.