Simple Examples

[philzook58]

3 simple examples where you can eyeball the optimal dag cost and can be scaled arbitrarily large.

1. AC to extract perfectly balanced trees
2. A list of binary choices where one choice has more sharing
3. A loop extraction example where you need a constraint to block extracting a loop instead of a term

[mwillsey]

This looks great @philzook58! What is up with the funky names and costs in the nodes json though? Is the "newer" exporting code in egglog doing this or could it perhaps generate better names?