OpenVPN: Add shortcuts in main profile view

[keeshux]

Some useful shortcuts can be replicated in the main profile screen.

Requirements:

• Modules implementing ModuleDestinationProviding return a navigationDestination() to navigate to module-specific routes (e.g. OpenVPN credentials). This was done in Move module destinations to standalone entities #1166
• In order to navigate to the module routes from the main ProfileCoordinator view, it must have a navigationDestination() attached for each of the modules, without knowing the concrete route types

Here is how this is accomplished in a generic fashion:

1. ProfileEditor.navigationDestinations() iterates over each ModuleDestinationProviding to return a list of navigationDestination(), implemented as a ViewModifier
2. With this in place, module routes can be pushed with a NavigationLink from the main profile view
3. Lastly, in the profile view, we add a section for each module implementing ModuleShortcutsProviding, where the module may return a list of convenient shortcuts, e.g. in the form of the NavigationLink in 2

Start with some OpenVPN entries:

• Provider server
• Credentials (if needed)

Some refactoring was necessary:

• Load ModulePreferences in the module destinations via ModulePreferencesModifier, rather than in the module view (may revisit later)
• Due to the above, move "Remote endpoints" from "Configuration" to a separate destination (also less messy)
• Group complex module views (OpenVPN/WireGuard) into folders
• Reuse ProviderServerRow for consistency across modules/shortcuts