Hide value label for opacity slider as well in color picker

[bjarnef]

Description

#1150 added a feature to hide value label for uui-color-slider and set this for hue slider, but not opacity slider.

I think it's a bit inconsistent it is show for opacity slider, but not hue slider:
https://uui.umbraco.com/?path=/story/uui-color-picker--opacity

and like this in CMS:

Ideally I think we should have a proper Tooltip component (not same as popover which may contain interactive elements) and possible it can be used for both uui-range-slider and uui-color-slider.

At the moment the specific opacity level can be seen in RGB(A) mode as well HEX(A) - although easiest in RGB(A) mode:

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (minor updates related to the tooling or maintenance of the repository, does not impact compiled assets)

Motivation and context

How to test?

Screenshots (if appropriate)

Checklist

• If my change requires a change to the documentation, I have updated the documentation in this pull request.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[github-actions]

Hi there @bjarnef, thank you for this contribution! 👍

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[Copilot]

Pull Request Overview

This PR hides the value label for the opacity slider in the color picker component by adding the hide-value-label attribute, matching the behavior of other sliders. Additionally, it reformats a CSS gradient definition for improved readability.

• Adds hide-value-label attribute to the opacity slider
• Reformats multi-line gradient CSS for better code readability

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud