[Ruby 3] Handle sorted_set removal in semantic_puppet gem

PUP-11047 handles the sorted_set removal from puppet, but this is also used in the semantic_puppet gem. There are a number of ways in which we can accomplish this:

• explicitly depend on the sorted_set gem and include it in puppet-runtime
• implement the functionality using the RbTreeMap class from puppet
• use the rbtree gem to implement the functionality (as suggested in https://github.com/puppetlabs/puppet/pull/8589#discussion_r631590428)