### 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
}
            }
            
            for (NamedExpression agg : aggs) {
                Expression e = agg instanceof Alias a ? a.child() : agg;
                if (e instanceof SurrogateExpression sf) {
                    changed = true;
                    Expression s = sf.surrogate();
                    
                    if (s instanceof AggregateFunction == false) {
                        
                        var surrogateWithRefs = s.transformUp(AggregateFunction.class, af -> {
                            
                            
                            var attr = aggFuncToAttr.get(af);
                            
                            if (attr == null) {
                                var temporaryName = temporaryName(agg, af);
                                
                                var newAlias = new Alias(agg.source(), temporaryName, null, af, null, true);
                                attr = newAlias.toAttribute();
                                aggFuncToAttr.put(af, attr);
                                newAggs.add(newAlias);
                            }
                            return attr;
                        });
                        
                        
                        
                        var aliased = new Alias(agg.source(), agg.name(), null, surrogateWithRefs, agg.toAttribute().id());