**Describe what's wrong**

Selecting from a Buffer table with ORDER BY <col> DESC clause returns wrong rows, and the returned rows are not ordered.

**Does it reproduce on recent release?**

Tested version: 22.7.2.15

**How to reproduce**

* Which ClickHouse server version to use
22.7.2.15
* `CREATE TABLE` statements for all tables involved

        CREATE TABLE mydb.mytable_stored
        (
            `a` UInt8
        )
        ENGINE = MergeTree
        ORDER BY a;

        CREATE TABLE mydb.mytable
        (
            `a` UInt8
        )
        ENGINE = Buffer('mydb', 'mytable_stored', 4, 600, 3600, 10, 100, 10000, 10000000);

* Sample data for all these tables
Note: rows must be inserted one-by-one:

        INSERT INTO mydb.mytable VALUES (0);
        INSERT INTO mydb.mytable VALUES (1);
        INSERT INTO mydb.mytable VALUES (2);
        INSERT INTO mydb.mytable VALUES (3);
        INSERT INTO mydb.mytable VALUES (4);
        INSERT INTO mydb.mytable VALUES (5);
        INSERT INTO mydb.mytable VALUES (6);
        INSERT INTO mydb.mytable VALUES (7);
        INSERT INTO mydb.mytable VALUES (8);
        INSERT INTO mydb.mytable VALUES (9);

* Queries to run that lead to unexpected result

        SELECT a FROM mydb.mytable ORDER BY a DESC LIMIT 5;
        ┌─a─┐
        │ 3 │
        │ 7 │
        └───┘
        ┌─a─┐
        │ 2 │
        │ 6 │
        └───┘
        ┌─a─┐
        │ 1 │
        └───┘
        5 rows in set. Elapsed: 0.007 sec.

(Interestingly, ascending order *seems* to work, did not test it thoroughly though.)

**Expected behavior**

Get the results in descending order, ie. `9, 8, 7, 6, 5`.

**Additional context**

Selecting the maximal value works:

        SELECT max(a) FROM mydb.mytable;
        ┌─max(a)─┐
        │      9 │
        └────────┘
        1 row in set. Elapsed: 0.007 sec.

After the rows are flushed to the backing MergeTree table, the results are good.

        OPTIMIZE TABLE mydb.mytable;
        SELECT a FROM mydb.mytable ORDER BY a DESC LIMIT 5;
        ┌─a─┐
        │ 9 │
        │ 8 │
        │ 7 │
        │ 6 │
        │ 5 │
        └───┘
        5 rows in set. Elapsed: 0.008 sec. 


return;
    }
    auto result_header = buffers_plan.getCurrentDataStream().header;
    
    if (!blocksHaveEqualStructure(query_plan.getCurrentDataStream().header, result_header))
    {
        auto convert_actions_dag = ActionsDAG::makeConvertingActions(
                query_plan.getCurrentDataStream().header.getColumnsWithTypeAndName(),
                result_header.getColumnsWithTypeAndName(),
                ActionsDAG::MatchColumnsMode::Name);
        auto converting = std::make_unique<ExpressionStep>(query_plan.getCurrentDataStream(), convert_actions_dag);
        query_plan.addStep(std::move(converting));
    }
    DataStreams input_streams;
    input_streams.emplace_back(query_plan.getCurrentDataStream());
    input_streams.emplace_back(buffers_plan.getCurrentDataStream());
    std::vector<std::unique_ptr<QueryPlan>> plans;
    plans.emplace_back(std::make_unique<QueryPlan>(std::move(query_plan)));
    plans.emplace_back(std::make_unique<QueryPlan>(std::move(buffers_plan)));
    query_plan = QueryPlan();
    auto union_step = std::make_unique<UnionStep>(std::move(input_streams));
    union_step->setStepDescription("Unite sources from Buffer table");
    query_plan.unitePlans(std::move(union_step), std::move(plans));
}
static void appendBlock(const Block & from, Block & to)
{
    size_t rows = from.rows();
    size_t old_rows = to.rows();
    size_t old_bytes = to.bytes();
    if (!to)