Consolidate evaluators for AlgebraicExpression

[georgwiese]

We currently have various places where we implement evaluating AlgebraicExpression. For example, there is one for each backend (e.g. Plonky3, Halo2, Stwo). Also, #2194 adds an ExpressionEvaluator that is used by the MockBackend and soon by the fast bus witgen as well (#2191).

I think we should consolidate them into one evaluator (could be a generalization of the ExpressionEvaluator mentioned above, see this comment). In addition to the current features (e.g. caching of intermediates), we should also add benchmarks and optimize performance.

Some ideas possible performance improvements:

• Use ColumnMap (a wrapper around Vec) instead of BTreeMap to store columns (the trace and the intermediates cache)
• Short-circuit multiplications by 0