A11y: Button order and semantics

Problem/Motivation

While working on #3528128, general questions about the buttons arose. We want to organize the work in this issue.

@rkoller wrote:

semantically, it feels odd to have a link element that is styled as a link but with a role of button. I consider it cleaner to use links for what they are made for, to point the user to another page, while buttons are used to let the user do something on the current page. if the element should be a button then i usually prefer to also use an actual button element - except overriding the markup by klaro would complicate things and it would be a jumping through hoops. :/
aside the question if a link or a button element is used in regard to semantics, i wonder what type of button should be used styling wise: a secondary button, a button or an action link? (for context see the drupal design system ) . It also feels odd to have two primary buttons (decline and accept) on the dialog, shouldn't it be only one primary button there?
In regard to the aural interface there is another detail to note, all the three buttons are missing a context, if a person is navigating by for example the rotor and gets only announced the available buttons on a page it is close to impossible to figure out the context for each button, and it should be avoided that a user has to inspect the close proximity of the element to learn about the context (check rotor.mp4 - close your eyes and try to make sense of things without the visual context). but the points about the styling and the labeling are probably out of scope for this issue.

Notice: The link cames from klaro_js and the Drupal modules adds an option to style the link like a button (not to replace the markup). But interesting: when using the notice as modal, "customize" is renedered as button.