feat: menu items hide actions

[JesmoDev]

Sets the width of the uui-menu-item action slot to 0 when not hovered or focused (previously just opacity)
This gives the text in the menu item more space, which is useful in narrow layouts.

Example of problem: There's a lot of wasted space on the right side of the menu-item

Example form Storybook
Before:

After:

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)

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.