[Install-unknown-apps] Hide apps of system or root UID

This also reverts ag/27176160, which handled apps like Settings but missed pre23 apps. A better solution would be hide apps that are of system or root UID.

BUG: 338066634
Test: manual

Change-Id: Ia1c3f50dd7c5edb718c695737db589ef55173682

src/com/android/settings/spa/app/specialaccess/InstallUnknownApps.kt

@@ -23,6 +23,7 @@ import android.app.AppOpsManager.MODE_DEFAULT
 import android.app.AppOpsManager.OP_REQUEST_INSTALL_PACKAGES
 import android.content.Context
 import android.content.pm.ApplicationInfo
+import android.os.Process
 import android.os.UserManager
 import androidx.compose.runtime.Composable
 import com.android.settings.R
@@ -94,7 +95,10 @@ class InstallUnknownAppsListModel(private val context: Context) :
         private fun isChangeable(
             record: InstallUnknownAppsRecord,
             potentialPackageNames: Set<String>,
-        ) = record.app.packageName in potentialPackageNames
+        ) =
+           record.app.uid != Process.SYSTEM_UID && record.app.uid != Process.ROOT_UID &&
+               (record.appOpsController.getMode() != MODE_DEFAULT ||
+                    record.app.packageName in potentialPackageNames)
 
         private fun getPotentialPackageNames(userId: Int): Set<String> =
             AppGlobals.getPackageManager()