Disallow turning off developer options in page-agnostic mode

When device is in page-agnostic mode, it would be OEM unlocked and
filesystem will be different than production. Don't allow to turn
off developer options in that state.

Bug: 329657279
Bug: 295035851
Test: m Settings && adb install -r $ANDROID_PRODUCT_OUT/system_ext/priv-app/Settings/Settings.apk
Change-Id: I9b8a9dbaf8192bb3758c53501450eb45e2fe8d9c