testing/kristall: upgrade to 0.3_git20210403

TODOs in the roadmap for 0.4 are not yet done https://github.com/MasterQ32/kristall/blob/master/ROADMAP.md

But there are plenty of changes and improvements since 0.3 release https://github.com/MasterQ32/kristall/compare/V0.3...master and this is in testing after all.