* Remove LegacyAnnotation and MoultingYaml

It has been deprecated since 1.1

* Remove all uses of ConvertLegacyAnnotations

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

- Old Annotation renamed to deprecated LegacyAnnotation
- Annotation is now a trait that can be extended
- New JsonProtocol for Annotation [de]serialization
- Replace AnnotationMap with AnnotationSeq
- Deprecate Transform.getMyAnnotations
- Update Transforms
- Turn on deprecation warnings
- Remove deprecated Driver.compile
- Make AnnotationTests abstract with Legacy and Json subclasses
- Add functionality to convert LegacyAnnotations of built-in annos
This will give a noisy warning and is more of a best effort than a
robust solution.

Fixes #475 Closes #609

Restricts annotations to be string-based (and thus less typesafe)
Makes annotations more easily serializable and interact with Chisel