Apply consistent concept for `navigation_app_site_name`

[defagos]

As a developer integrating Pillarbox I would like to have a common understanding of configuration parameters between platfiorms.

Acceptance criteria

• The name of the configuration parameter for navigation_app_site_name has been discussed (hint: A proposal was product instead of the current site name).
• Dedicated implementation tasks have been created if needed.

Tasks

• [x] Discuss name.
• [x] Create implementation tasks (work + documentation update) if needed.

[defagos]

Reports mention App / Site Name so to avoid confusion we should likely interpret it as Application or site name and call it appSiteName in our API:

This way we stick to the current naming conventions and avoid confusion.

[defagos]

A dedicated issue has been created for Apple platforms (see link above). The Android implementation has been updated as part of other changes. Closed.