Support dexopt for incremental apps in ART Service.

This change adds an additional condition to make ART Service write
artifacts to the global dalvik-cache directory for incremental apps
because they are in the readonly Incremental FS.

Bug: 270454539
Test: atest ArtServiceTests
Test: -
  1. Install a normal app.
  2. Dexopt the app and see the artifacts next to the APK.
Test: -
  1. Install an incremental app. (`adb install` an app that comes with a
     .idsig file)
  2. Dexopt the app and see the artifacts in dalvik-cache.
Ignore-AOSP-First: ART Services
Change-Id: Ie74d50cf3f012fef894cc71caf6cfcfff0b4fb61