### Description

Evals that introduce aliased can be simplified by extracting them into a project (and thus signaling there's no underlying processing).

The following eval:
`eval x = a + 1, y = x, z = y + 1, y = z, w = y + 1`
can be converted into:
`eval x = a + 1, z = a + 1 + 1, w = a + 1 + 1 | project x, z, z as y, w`

This helps fuse the project with other projections/aggs downstream.
x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/LogicalPlanOptimizer.java
public LogicalPlan optimize(LogicalPlan verified) {
        return verified.optimized() ? verified : execute(verified);
    }
    @Override
    protected List<Batch<LogicalPlan>> batches() {
        return rules();
    }
    protected static List<Batch<LogicalPlan>> rules() {
        var substitutions = new Batch<>("Substitutions", Limiter.ONCE, new SubstituteSurrogates(), new ReplaceRegexMatch()
        
        );
        var operators = new Batch<>(
            "Operator Optimization",
            new CombineProjections(),
            new CombineEvals(),
            new PruneEmptyPlans(),
            new PropagateEmptyRelation(),
            new ConvertStringToByteRef(),
            new FoldNull(),
            new SplitInWithFoldableValue(),
            new ConstantFolding(),
            new PropagateEvalFoldables(),