Summary: Up till now, `AstStorage` also took care of tracking the root of the `Query` and loading of cloning of `Query` nodes would change that root. This felt out of place because sometimes `AstStorage` is used only for storing expressions, and we don't even have an entire query in the storage. This diff removes that feature from `AstStorage`. Now its only functionality is owning AST nodes and assigning unique IDs to them.
Reviewers: teon.banek, llugovic
Reviewed By: teon.banek
Subscribers: mferencevic, pullbot
Differential Revision: https://phabricator.memgraph.io/D1646