Rename from community.kubernetes to kubernetes.core (#6)

* Rename from community.kubernetes to kubernetes.core

This goes through and renames community.kubernetes to kubernetes.core.
Most of this was generated from the downstream build script that was
used on the community repository, plus whatever hand edits I could find
that were needed.

The downstream build and test process has also been removed as this
repository is now the downstream repository.

* Fix CONTRIBUTING.md

galaxy.yml

@@ -12,12 +12,12 @@ dependencies: {}
 description: Kubernetes Collection for Ansible.
 documentation: ''
 homepage: ''
-issues: https://github.com/ansible-collections/community.kubernetes/issues
+issues: https://github.com/ansible-collections/kubernetes.core/issues
 license_file: LICENSE
-name: kubernetes
-namespace: community
+name: core
+namespace: kubernetes
 readme: README.md
-repository: https://github.com/ansible-collections/community.kubernetes
+repository: https://github.com/ansible-collections/kubernetes.core
 tags:
   - kubernetes
   - k8s