feat(OnyxSlider): stabilize component API

[larsrickert]

Relates to #4457

OnyxUnstableSlider is renamed to OnyxSlider and is now considered to have a stable API.
Therefore, no breaking changes will be introduced from now on within major versions. The OnyxUnstableSliderControl component has been removed and integrated into the OnyxSlider directly.

Changes to the last unstable version:

• when control="icon" is set, the icon buttons will no longer be focusable via keyboard because its redundant (slider can already be changed with arrow keys). When clicking the icon buttons, the tooltip will now be shown automatically
• when labelled marks are used, the tooltip will now be positioned top
• remove disableTooltip property in favor of new tooltip property that also allows customizing the tooltip value
• removed errorMessages and successMessages property which were inconsistent with other form components. Use error and success instead
• fix: error message not shown when slider is touched

Checklist

• The added / edited code has been documented with JSDoc
• If a new component is added, at least one Playwright screenshot test or functional test is added
• A changeset is added with npx changeset add if your changes should be released as npm package (because they affect the library usage)
• I have performed a self review of my code ("Files changed" tab in the pull request)
• All relevant changes are documented in the documentation app (folder apps/docs) if needed

[changeset-bot]

🦋 Changeset detected

Latest commit: 874dafc

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@sit-onyx/headless	Minor
sit-onyx	Minor
@sit-onyx/chartjs-plugin	Major
@sit-onyx/nuxt-docs	Major
@sit-onyx/nuxt	Major
@sit-onyx/vitepress-theme	Major

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