OGM-522 Cache Neo4j CRUD queries

https://hibernate.atlassian.net/browse/OGM-522

Queries get created during the schema definition and injected in the dialect using a map.

The dialect can get the queries using EntityKeyMetadata or AssociationKeyMetadata as keys.
Can we make it

    this.associationQueries = Collections.unmodifiableMap( initializeAssociationQueries( sessionFactoryImplementor ) );