Adjust the releases process documentation. (#10727)

* markdown numbered lists: no need to manually maitain the numbers

* add instructions to update the collection version roughly following
  Ansible collection maintenance guidelines
  (https://docs.ansible.com/ansible/latest/community/collection_contributors/collection_release_with_branches.html)

* Distinguish major from minor releases in the release process

* Bump current galaxy.yml version to the next release