We extract the compliance_tool into its own
package, since the functionality is not needed
in the general SDK anymore.

The new aas-compliance-tool can be found
[here](https://github.com/rwth-iat/aas-compliance-tool).

When we removed the schema files, we overlooked
that JSON and XML serialization need them.
We probably need to find a way of fetching
them during runtime of the test to avoid having
to host them in our repository.

This removes the JSON Schema and XSD files that
stem from the aas-specs repository.
Instead, this adds the logic in the CI to fetch
these files at runtime.

Furthermore, we skip the unittests that make use
of the schema files when they do not exist.