### 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
""");
        assertThat(plan, instanceOf(LocalRelation.class));
    }
    public void testFoldNullListInToLocalRelation() {
        LogicalPlan plan = optimizedPlan("""
            from test
            | where first_name in (null, null)
            """);
        assertThat(plan, instanceOf(LocalRelation.class));
    }
    public void testFoldInKeyword() {
        LogicalPlan plan = optimizedPlan("""
            from test
            | where "foo" in ("bar", "baz")
            """);
        assertThat(plan, instanceOf(LocalRelation.class));
        plan = optimizedPlan("""
            from test
            | where "foo" in ("bar", "foo", "baz")
            """);
        var limit = as(plan, Limit.class);
        as(limit.child(), EsRelation.class);
    }
    public void testFoldInIP() {
        LogicalPlan plan = optimizedPlan("""
            from test
            | where to_ip("1.1.1.1") in (to_ip("1.1.1.2"), to_ip("1.1.1.2"))
            """);
        assertThat(plan, instanceOf(LocalRelation.class));
        plan = optimizedPlan("""