A small exercise to see whether we can run ES|QL queries from unit or csv tests against actual Lucene indices.

• Factor out query execution code from CsvTests into the new class TestQueryRunner.
• Add OptimizerExecutabilityTests which executes an optimized plan against a Lucene index, using the actual EsPhysicalOperationProviders.

The latter uses MapperServiceTestCase.withLuceneIndex together with the fact that executing an ES|QL query requires

• the optimized query,
• physical operation providers, built from a search execution context (that's what we need withLuceneIndex for), and
• index and enrich resolutions.