Add Tensat Examples

[ezrosent]

This PR adds some examples from Tensat. The Tensat repo dynamically estimates costs of certain operators based on the hardware on which it is run. I wrote some code to "scrape" these costs and then write them to the extraction-gym format.

A couple notes on this one:

• The "bottom-up" algorithm appeared to infinite-loop for the nasneta examples here. I dug into this a bit and found that we were spending all of the time in tree_cost: the fix is to memoize duplicate calls in tree_cost and dag_cost. Things finish pretty fast after that.
• One lesson from that paper is that ILPs can be encoded "naively" (without any constraints around cycles) if the e-graph is pruned ahead of time. The "acyclic" examples here include the results of that process.

[mwillsey]

I'm changed the format, but hopefully you can use the convert.py script to easily convert to the new format.

[ezrosent]

Will do! Need to re-merge some of the memoization stuff but that actually looks like it'll be easier to add with the new structure. I should have it done soon.

[ezrosent]

Should be good to go!

[mwillsey]

@ezrosent do you recall the pruning process? #14 notices some cycles present in even the _acyclic variants.

[ezrosent]

I just used https://github.com/uwplse/tensat + the sample code for exporting egg to the extraction-gym format. I don't think I modified tensat at all.

Maybe some of the cycle pruning happens during extraction in tensat? It's also possible that I invoked the tool incorrectly (though the acyclic variants are smaller here, so something is happening at least).

[ezrosent]

I can try and dig up the specific setup I had that generated this (old windows machine with an nvidia GPU), but in the near-term, we can probably just remove the _acyclic egraphs that have cycles in them?