Implementation of schema build functionality that enable the maintenance of schema modules instead of a single large schema specification

[jh-RLI]

Description of the issue

The schema.json that is part of each oemetadata release becomes more and more complex. It would be better to introduce modules that only hold parts of the schema content. Therefore we need a process that can resolve & merge the modules into its complete state by assembling the parts.

Ideas of solution

• [x] introduce a new folder / folders to implement the build process
• [x] devide the current schema into modules
• [x] each part should (of the modul) should only contain one level of nesting (maybe except for lists)
• [x] the result must be equal to the current schema.json
• [ ] there must be a test that check if every schema within a release is valid with the result of the build.

Workflow checklist

• [ ] I am aware of the workflow in CONTRIBUTING.md