[v2.0] Move node name checking in tree_node to relevant policies

[cmannett85]

In an ideal world, all the policies and nodes would be 'opaque' such that all the policies form a hemetic parse pipeline (i.e. only the input tokens are considered) as that would be sinplest/cleanest architecture. Unfortunately it would prevent policies/nodes being able to query others, greatly reducing their power.

However we should still strive towards that. As a start we move the node name checking from the tree_node into the corresponding policies.