Replace `dbc.Button` with `dbc.Link` in Navigation

Description

Replace dbc.Button with dbc.Link in Accordion, NavLink and NavBar
Removed active_page_id where possible (it's still present in some builds - see explanation here: https://github.com/mckinsey/vizro/pull/326#discussion_r1497505109)

Context: Changes are necessary to ensure the use of semantically correct elements in the DOM, which is advantageous for HTML documents in general. This approach also proves beneficial when implementing a Bootstrap theme. Previously, the navigation erroneously adopted the primary button color when incorporating a Bootstrap theme. By utilizing the appropriate elements, we ensure that the correct coloring is applied based on the intended HTML element.

For our future selves to understand the decisions made here:

Screenshot

Notice

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mckinsey / vizro