Extract egraph-serialize features

[DaniPopes]

egraph-serialize's "serde" and "graphviz" features are not used in the library but are always enabled. Disable them by default and extract them into our own features that just delegate to egraph-serialize to preserve the functionality.

This is a breaking change for library users that disable default features.

[codspeed-hq]

CodSpeed Performance Report

Merging #466 will not alter performance

_{Comparing DaniPopes:serialize-features (6a830c5) with main (2c8d947)}

Summary

✅ 8 untouched benchmarks

[saulshanabrook]

That makes sense to me, thanks for the warning on the possible downstream breakage.