Summary:
Add EdgeList symbol type and check for redeclaration
The result of variable path is a list of edges, so the symbol type has
been added. In the future, we need to extend the type checker and the
type structure to have a generic list type.
We also currently do not support reusing an already bound symbol for a
variable path, so the SymbolGenerator will raise a redeclaration error.
Reviewers: florijan, mislav.bradac
Reviewed By: mislav.bradac
Subscribers: pullbot, lion
Differential Revision: https://phabricator.memgraph.io/D574
da7bfe05b7