Improvements to `lf.eval` framework.

[copybara-service[bot]]

Improvements to lf.eval framework.

• Show OOP and non-OOP failures separately (both summary and detailed page)
• Group failure details by error types.
• Better error handling for dryrun mode.
• Introduced Evaluation.visualize method, allowing users to plugin custom HTML views (e.g. matplot) for generating the summary page.
• Included usage in summary.json.