chore(weave): add F1 and Accuracy scorers

[rymc]

Added an accuracy and F1 scorers both for single task evaluations but also multitask evaluations.

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[rymc]

I have read the CLA Document and I hereby sign the CLA

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[scottire]

@rymc (nice vanity username btw) do you have examples you've been using to test these? They'd be good to have so users can see how to use them, and it'll help us add docs and make sure we don't introduce regressions if they're changed