[World Logs] Don't crash if a value can't be serialized

[spencerp]

Patch description
text_vec and full_text_vec in the observations contain tensor and can't be json serialized in eval_model --world-logs. In this type of scenario, if we crash, we lose all of the logs and have to rerun. This fails more gracefully.

Testing steps

>>> d = {'a': tensor}
>>> json.dumps(d, default=lambda v: '<not serializable>')
'{"a": "<not serializable>"}'

[stephenroller]

hmm i guess this is good, vaguely wish we could filter instead of dumping a thousand "not serializable" strings

[spencerp]

hmm i guess this is good, vaguely wish we could filter instead of dumping a thousand "not serializable" strings

We could filter them. My thought was that it'd be useful to have this feedback in case you did want a field but forgot to convert it into a serializable form. Like if you put in a metric but forgot to call .value.

[stephenroller]

We can go with this and see if gets in the way