Cli: parsing multiple times throws `AlreadySelectedException`

This issue has been fixed in commons-cli:1.3 project which sadly has not been released yet.
See https://issues.apache.org/jira/browse/CLI-183

This patch builds another list of options with no selected groups by default.

When commons-cli:1.3 will be released, we need to remove this patch.

Closes #7282.
Aggregations: Add `children` bucket aggregator that is able to map buckets between parent types and child types using the already builtin parent/child support.

Closes #6936