New text2sql metrics

[oktie]

The goal is to add additional metrics and results to the output of the text2sql execution accuracy metric implementation. We used to produce just one number: 1 if the dataframe produced by the SQLs in pred and gold are the same, 0 otherwise. I've added scores to report 12 scores/outputs:

1. execution_result: if df responses match (same as before)
2. non_empty_execution_result: if dfs are non-empty and match
3. subset_non_empty_execution_result: if non-empty dfs and gt df subset of predicted df
4. non_empty_gold_df: if gt df is non-empty
5. gold_sql_runtime: ground truth query runtime
6. predicted_sql_runtime: predicted query runtime
7. pred_to_gold_runtime_ratio: ratio of predicted query runtime to gt query runtime
8. gold_error: if gt has an error
9. predicted_error: if predicted query has an error
10. ground truth dataframe
11. predicted query's dataframe
12. error message (if any)

What we used to get (output of examples/evaluate_text2sql.py):

num_of_instances (int):
    10
anls (float):
    0.12179476763080924
score (float):
    0.2
score_name (str):
    execution_accuracy
execution_accuracy (float):
    0.2
execution_accuracy_ci_low (float64):
    0.0
execution_accuracy_ci_high (float64):
    0.6
score_ci_low (float64):
    0.0
score_ci_high (float64):
    0.6

What we get with the new additions:

num_of_instances (int):
    10
anls (float):
    0.12179476763080924
score (float):
    0.0
score_name (str):
    non_empty_execution_accuracy
non_empty_execution_accuracy (float):
    0.0
subset_non_empty_execution_result (float):
    0.0
pred_to_gold_runtime_ratio (float):
    0.9950211077562516
predicted_error (float):
    0.1
predicted_sql_runtime (float):
    0.8206439448520542
gold_error (float):
    0.0
non_empty_gold_df (float):
    0.0
gold_sql_runtime (float):
    0.8285779342986643
execution_accuracy (float):
    0.2
predicted_sql_runtime_ci_low (float64):
    0.7456668988301784
predicted_sql_runtime_ci_high (float64):
    1.0325724025184853
gold_sql_runtime_ci_low (float64):
    0.7711773584951769
gold_sql_runtime_ci_high (float64):
    0.9317167796579513
execution_accuracy_ci_low (float64):
    0.0
execution_accuracy_ci_high (float64):
    0.6

[oktie]

To resolve some merge conflicts, I'm closing this and will do a new PR.