Handling namespaces of embedded types correctly

[nick-zh]

It was discovered (@bajdzun ), that the SR does not include namespaces of subtypes when they are in the same space.
To cover this a new option --optimizeSubSchemaNamespaces was added (#5, #10) to make this possible without breaking the current behaviour.
Upon further investigation it seems this is part of the Avro specification and should be default behaviour, see discussion in (#12).
This will be properly addressed and will result in a major release.

Thanks @bajdzun, @healerz & co for the help and uncovering this issue 🙏

[nick-zh]

After some discussions and research, it seems both ways are fine and accepted by Avro. The SR does not optimize namspaces when you register schemas, so the decision was to keep the behaviour as a flag, but name mit more closely to Avro wording --optimizeFullNames. An additional flag --optimizeFieldOrder was added, that orders the fields the same as AvroSchema::parse