[client-v2, jdbc-v2] Add MultiPoint type support

Follow-up to [#2577](https://github.com/ClickHouse/clickhouse-java/issues/2577). At the time it was noted that ClickHouse has no `MultiPoint` type:

> ClickHouse doesn't support `GeometryCollection`, `MultiPoint`. Here is link for supported types https://clickhouse.com/docs/sql-reference/data-types/geo
>
> There is a `Ring` what may be a `MultiPoint`.
>
> _Originally posted by @chernser in [#2577](https://github.com/ClickHouse/clickhouse-java/issues/2577#issuecomment-3321276471)_

That has since changed on the server side. `MultiPoint` is now a first-class geo type [documented on that same page](https://clickhouse.com/docs/sql-reference/data-types/geo), defined as `Array(Point)`, and `Geometry` is documented as a common type for all the geo types listed there.

**Note on versions:** this is a heads-up, not a regression report. `MultiPoint` is not in 26.7 or earlier — I'm testing against a master/head build (`26.8.1.146`), so it should land in the next release. Filing now so client support can be in place before then.

The client already ships `Geometry` support ([#2815](https://github.com/ClickHouse/clickhouse-java/pull/2815)) for CH 25.11+, where `Geometry` became `Variant(Point, Ring, LineString, MultiLineString, Polygon, MultiPolygon)`. `MultiPoint` appears to be the one geo type left out of both the concrete-type path and that variant list.

`GeometryCollection` remains correctly out of scope — `Geometry` is the ClickHouse equivalent.

## Reproduction

```sql
CREATE TABLE geo_multipoint (mp MultiPoint) ENGINE = Memory();
INSERT INTO geo_multipoint VALUES([(0, 0), (10, 0), (10, 10), (0, 10)]);
SELECT mp, toTypeName(mp) FROM geo_multipoint;

-- via WKT, and through the unified type
SELECT readWKT('MULTIPOINT(0 0, 10 0, 10 10)') AS mp, toTypeName(mp);
CREATE TABLE geo_any (g Geometry) ENGINE = Memory();
INSERT INTO geo_any SELECT readWKT('MULTIPOINT(0 0, 10 0, 10 10)');
SELECT g, toTypeName(g) FROM geo_any;
```

**Expected:** `MultiPoint` is recognised as a geo column type and returned in the same geometry-aware representation the other geo types got after [#2581](https://github.com/ClickHouse/clickhouse-java/pull/2581), and it round-trips on insert.

**Actual:** reading a `MultiPoint` column via jdbc-v2 gives:

```
Caused by: java.lang.IllegalArgumentException: Unsupported data type: MultiPoint
```

## Proposed changes

- [ ] Add `MultiPoint` to the ClickHouse data-type enum / type parser.
- [ ] Read path: map `MultiPoint` to the same geometry representation used for `Ring` / `LineString` (both are also `Array(Point)`).
- [ ] Write path: support inserting `MultiPoint`, including via `readWKT` / WKB round-trip.
- [ ] JDBC metadata: `getColumnType` / `getColumnTypeName` / `getColumnClassName` for `MultiPoint` columns, so v2 doesn't NPE the way the types in [#2711](https://github.com/ClickHouse/clickhouse-java/issues/2711) did.
- [ ] Extend `Geometry` variant handling if the server includes `MultiPoint` in it.

## Environment

- clickhouse-java: 0.9.8
- Driver: jdbc-v2 / client-v2
- ClickHouse server: 26.8.1.146 (master/head build — not a stable release)