WIP: Rewrite & improve DSL and equality saturation code

[Colton1skees]

• Rewrite equality saturation code from scratch
  • Use the same AST both inside of and outside of the egraph, solving a bunch of outstanding problems (conversion overhead, code duplication, syncing analyses in and out of the egraph)
  • Implement conversion from our term rewriting DSL to egg's DSL
• Extend AST with icmp and select nodes. Update the rest of the codebase to handle these nodes
• Extend term rewriting DSL to support preconditions, functions, and intrinsics.
• Misc changes