Add package to Intent#saveToXml

Current version does not pass filterEquals on itself due to package
not getting persisted so add package.

Test: verify manually that saveToXml->restoreFromXml passed filterEquals, new test
Bug: 369856202
Flag: android.content.flags.intent_save_to_xml_package
Change-Id: I7ce1bbe1b2274157e8f0af214f4327ad1ea1cb08