[BUG] Cache management failed for tasks using sample_params to update function attrs

## Describe the bug
Metric:__call__ used "&".join(f"{k}={v}" for k, v in sample_params.items()) to update metric name, but the value might be function, which will change for each run.

## To Reproduce
Task that use sample_params, such as:
leaderboard:gsm8k:0

metrics=[
Metrics.exact_match(sample_params={"normalize_gold": gsm8k_normalizer, "normalize_pred": gsm8k_normalizer})
],

## Expected behavior
Cache should work

## Version info
main branch