### 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/test/java/org/elasticsearch/xpack/esql/optimizer/LogicalPlanOptimizerTests.java
}
    private LogicalPlan optimizedPlan(String query) {
        return plan(query);
    }
    private LogicalPlan plan(String query) {
        var analyzed = analyzer.analyze(parser.createStatement(query));
        
        var optimized = logicalOptimizer.optimize(analyzed);
        
        return optimized;
    }
    private void assertNullLiteral(Expression expression) {
        assertEquals(Literal.class, expression.getClass());
        assertNull(expression.fold());
    }
    
    private static FieldAttribute getFieldAttribute(String name) {
        return getFieldAttribute(name, INTEGER);
    }
    private static FieldAttribute getFieldAttribute(String name, DataType dataType) {
        return new FieldAttribute(EMPTY, name, new EsField(name + "f", dataType, emptyMap(), true));
    }
    public static WildcardLike wildcardLike(Expression left, String exp) {
        return new WildcardLike(EMPTY, left, new WildcardPattern(exp));
    }
    public static RLike rlike(Expression left, String exp) {
        return new RLike(EMPTY, left, new RLikePattern(exp));
    }
}