Refactor: Add an icon "size" prop to the minipipeline component

Description

Currently the size of the minipipeline component is determined by the CSS classes that surround the mini pipeline. This depends on CSS classes to be set correctly, while the icons that are rendered have a wrong size attached to them.

Minipipeline in MR Widget, 24px:

Minipipelines in pipelines list, 22px:

Proposal

Add a new e.g. :size="22" to the stage.vue component (or another similar to it) to remove the CSS classes and pass these values directly to the icon below.

Discussion

The following discussion from !53596 (merged) should be addressed:

• @mrincon started a discussion:

  This size could be made explicit by the mini-pipeline components (stage.vue) so their clients can set the size they need as we do with icons, that way we won't have competing CSS rules.