### 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
}
            return plan.order().size() == order.size() ? plan : new OrderBy(plan.source(), plan.child(), order);
        }
    }
    private static Project pushDownPastProject(UnaryPlan parent) {
        if (parent.child() instanceof Project project) {
            AttributeMap.Builder<Expression> aliasBuilder = AttributeMap.builder();
            project.forEachExpression(Alias.class, a -> aliasBuilder.put(a.toAttribute(), a.child()));
            var aliases = aliasBuilder.build();
            var expressionsWithResolvedAliases = (UnaryPlan) parent.transformExpressionsOnly(
                ReferenceAttribute.class,
                r -> aliases.resolve(r, r)
            );
            return project.replaceChild(expressionsWithResolvedAliases.replaceChild(project.child()));
        } else {
            throw new EsqlIllegalArgumentException("Expected child to be instance of Project");
        }
    }
    /**
     * Combine disjunctions on the same field into an In expression.
     * This rule looks for both simple equalities:
     * 1. a == 1 OR a == 2 becomes a IN (1, 2)
     * and combinations of In
     * 2. a == 1 OR a IN (2) becomes a IN (1, 2)
     * 3. a IN (1) OR a IN (2) becomes a IN (1, 2)
     *
     * This rule does NOT check for type compatibility as that phase has been
     * already be verified in the analyzer.
     */
    public static class CombineDisjunctionsToIn extends OptimizerRules.CombineDisjunctionsToIn {