[arteval] Improving the validation oracles code and workflow

[xuafeng]

Thanks @xuafeng -- please see my comment below.

[bastoica]

This is an umbrella task to track significant improvements and bug fixing related to ArtEvalBench's agent validation oracles.

Tasks:

• Significant refactoring that standardizes oracle validation: [arteval] Major refactoring: implementing standardized and reusable validation oracle primitives #107
• Fix oracle primitives inconsistencies: Fix inconsistent oracle primitives #117 and [arteval] bugfix: Fixing multiple logical bugs, and some refactoring #118
• Fixing bugs in WASABI's validation oracles: [arteval] Bugfix for WASABI #120
• Fixing bugs in EGWALKER's validation oracles: [arteval] Bugfix for EGWALKER #126