Add setting to toggle automatic sign in (#538)

## Description
The major user facing change in this PR is adding back the setting to
toggle automatic sign in on or off. This controls whether to restore the
app to where you left off or go the user selection page.

If enabled: re-opening the app will restore the previous user's session

If disabled: re-opening the app will always start with the user
selection page for the most recent server, or if there isn't a recent
server, the server selection page

This also separate this setting from the PIN protection settings in
previous PRs.

### Dev changes

This PR refactors the "setup" UI (server & user selection) to be
separate from the "app" UI (the actually app content). There is now a
`NavDisplay` for the setup flow which ends with displaying the
`ApplicationContent`'s `NavDisplay`. Most of the logic is moved out of
Compose code and into a `ViewModel`.

This means to switch users/server, the `SetupNavigationManager` must be
used instead of `NavigationManager`.


### Related issues
Closes #396
Fixes #376

app/src/main/java/com/github/damontecres/wholphin/preferences/AppPreference.kt

@@ -851,8 +851,7 @@ val basicPreferences =
             title = R.string.ui_interface,
             preferences =
                 listOf(
-                    // TODO PIN-related
-                    // AppPreference.SignInAuto,
+                    AppPreference.SignInAuto,
                     AppPreference.HomePageItems,
                     AppPreference.CombineContinueNext,
                     AppPreference.RewatchNextUp,