Add an experimental e-graph equality saturation framework for KQIR optimizer

[PragmaTwice]

Search before asking

• [X] I had searched in the issues and found no similar issues.

Motivation

As e-graphes are great tool for equality saturation in program optimizer to perform term rewriting, we can build them as a builtin framework for KQIR optimizer to generate better query plans.

Solution

No response

Are you willing to submit a PR?

• [X] I'm willing to submit a PR!