Use attributes for rule XML

Make use of XML attributes to respresent rules in parsing and
serializing, which would have a positive size impact on rule files.

Bug: 143697198
Test: atest FrameworksServicesTests:RuleXmlParserTest
Test: atest FrameworksServicesTests:RuleXmlSerializerTest
Change-Id: Ie7c7d3df05e29813c7979050621cf6c15857c582
4 files changed