### 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
""");
        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 limit = as(extractRest.child(), LimitExec.class);
        var filter = as(limit.child(), FilterExec.class);
        var eval = as(filter.child(), EvalExec.class);
        var fieldExtract = as(eval.child(), FieldExtractExec.class);
        assertEquals(EsQueryExec.class, fieldExtract.child().getClass());
        var source = source(fieldExtract.child());
        assertThat(source.estimatedRowSize(), equalTo(allFieldRowSize + Integer.BYTES + KEYWORD_EST));
    }
    public void testPushDownLike() {
        var plan = physicalPlan("""
            from test
            | where first_name like "*foo*"
            """);
        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());
        assertThat(source.estimatedRowSize(), equalTo(allFieldRowSize + Integer.BYTES));
        QueryBuilder query = source.query();
        assertNotNull(query);
        assertEquals(WildcardQueryBuilder.class, query.getClass());
        WildcardQueryBuilder wildcard = ((WildcardQueryBuilder) query);