Upgrade to reasoner-validator 4.0.1 (Pydantic V2) plus some tech debt

• update to reasoner-validator 4.0.1 (which uses Pydantic 2)
• remove reasoner-pydantic; delete the graph_validation_test.requests (which used reasoner-pydantic) an graph_validation_test.utils.testsuite modules (both unused legacy modules copied over from Benchmarks for coding inspiration)
• change some logger messages to 'debug' (from 'info')