Remove eval and rework primitive extraction

[saulshanabrook]

This PR reworks how primitives are extracted. Previously you would use egraph.eval(x) if x is a primitive like an i64 to get the python int value from it. This used some private methods of the egraph at runtime to inspect the rust value.

Instead, we now just extract the primitive and use python to "parse" it from the AST. So this also works for things like vecs. This adds support for python builtin methods like int and list so they can be used to implicitly extract things from the egraph:

>>> from egglog import *
>>> i64(1) + 2
i64(1) + 2
>>> int(i64(1) + 2)
3
>>> Vec(i64(1)).push(i64(2))
Vec(1).push(2)
>>> list(Vec(i64(1)).push(i64(2)))
[i64(1), i64(2)]

To do this, we refine the concept of a "current" e-graph in the context. If none exists, one will be created. But we can use one with the egraph.set_current() context manager.

We also add support for translating == into eq and != into ne for all types. If you need to override these operations on your type, you still can, and then just use the functions.

[codspeed-hq]

CodSpeed Performance Report

Merging #265 will not alter performance

_{Comparing current_egraph (87edb7d) with main (af2cdc8)}

Summary

✅ 8 untouched benchmarks