feat: Distinct styling for anchors without href

[rolfsmeds]

Flow intends to use (temporary) href attribute removal to disable anchors (as they lack a native disabled state), see vaadin/flow#10924. This PR changes Lumo styling of anchors so that the regular styling is applied only to anchors with href (using the :any-link pseudoclass) and Lumo disabled text color is instead applied to those without.

Potential breaking change: if an app contains href-less anchors (and e.g. use click event to do stuff instead) they will now have a disabled text color. However, at least Flow apps are almost guaranteed to have an empty href rather than missing one (unless developer has explicitly removed the empty href), so this is very unlikely to affect Flow-based apps.

Fixes #1594

Type of change

• Bugfix
• Feature

Checklist

• I have read the contribution guide: https://vaadin.com/docs-beta/latest/guide/contributing/overview/
• I have added a description following the guideline.
• The issue is created in the corresponding repository and I have referenced it.
• I have added tests to ensure my change is effective and works as intended (not really testable until Flow fix is in)
• New and existing tests are passing locally with my change.
• I have performed self-review and corrected misspellings.

Additional for Feature type of change

• Enhancement / new feature was discussed in a corresponding GitHub issue and Acceptance Criteria were created.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

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[vaadin-bot]

This ticket/PR has been released with platform 23.0.0.