Group generated types

[bdunogier]

Add support for grouping of types in the schema generator. For now, it generates one file per type. It could be lowered by grouping items:

• all content types in one file
• all types (domain content, content type, inputs, connection...) from a Domain Content Type in one file: ArticleContent.types.yml, BlogPostContent.types.yml
• blocks in one file

With this, the amount of files should remain manageable.

[bdunogier]

Could be done in the Builder layer, as we have one per domain item: DomainContentSchemaBuilder, PageSchemaBuilder, FormSchemaBuilder...

It still requires that the command is aware of that structure, and is able to distinguish it from the actual types.