Improve markdown editor modularity and structure

[guerler]

Extracted from #19775. This PR contains various improvements to the markdown editor:

1. Migrate Markdown templates and requirements from JSON to YAML.
2. Ensure consistent parsing and handling of workflow labels.
3. Upgrade visualization packages to the latest versions.
4. Change the default setting for markdown-compatible/embeddable visualizations in the visualization XML from true to false. Developers must now explicitly enable this option for visualizations to appear in the markdown toolbox, preventing unintended listings due to a missing setting.
5. Contains a fix for the Vega wrapper fixing the reactivity
6. Various minor fixes for Markdown components and additional tests
7. Adjust layout of final Markdown display page, fixes wrong update time, add margin to allow scrolling (without it users might get stuck zooming into visualizations instead)

Before:

After:

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[davelopez]

The refactoring looks good to me. Some very minor comments below.

[davelopez]

I've seen this type re-defined in several places (WorkflowLabelKind), it would be nice to have a single type definition in a common place as a single source of truth.

[guerler]

Thank you, I will consolidate these in a follow-up.

[guerler]

@davelopez thank you so much for the review!