Handle density configuration changes to prevent unnecessary app restarts (#1828)

## Description
Add `density` to `configChanges` and handle any changes to density that
occur. Thankfully, Compose handles density changes itself, so only
changes where a density calculation is "remembered" needed to be
updated.

Without this, some devices will recreate `MainActivity` when switching
resolutions for playback. That recreation would cause playback to end
immediately.

### Related issues
Fixes #1809

### Testing
Tested on Onn 4k Pro & nvidia shield

I was able to reproduce on the Onn, but not the Shield, so this might be
device and/or API level specific

## Screenshots
N/A

## AI or LLM usage
None

app/src/main/java/com/github/damontecres/wholphin/MainActivity.kt

@@ -380,7 +380,7 @@ class MainActivity : AppCompatActivity() {
 
     override fun onConfigurationChanged(newConfig: Configuration) {
         super.onConfigurationChanged(newConfig)
-        Timber.d("onConfigurationChanged")
+        Timber.d("onConfigurationChanged: newConfig=%s", newConfig)
     }
 
     override fun onNewIntent(intent: Intent) {