### 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/PhysicalPlanOptimizerTests.java
assertThat(rqb.from(), is(60_000));
    }
    
    
    
    
    
    
    
    
    public void testPushDownRecombinedIn() {
        var plan = physicalPlan("""
            from test
            | where "Pettey" in (last_name, "Simmel") or last_name == "Parto"
            """);
        var optimized = optimizedPlan(plan);
        var topLimit = as(optimized, LimitExec.class);
        var exchange = asRemoteExchange(topLimit.child());
        var project = as(exchange.child(), ProjectExec.class);
        var extractRest = as(project.child(), FieldExtractExec.class);
        var source = source(extractRest.child());
        var tqb = as(sv(source.query(), "last_name"), TermsQueryBuilder.class);
        assertThat(tqb.fieldName(), is("last_name"));
        assertThat(tqb.values(), is(List.of("Pettey", "Parto")));
    }
    /**
     * Expected:
     *  LimitExec[10000[INTEGER]]
     *  \_ExchangeExec[REMOTE_SOURCE]
     *    \_ExchangeExec[REMOTE_SINK]