Expose HTTP response message (or response metadata) for ClickHouseRawResult

### Use case
When using ClickHouseRawResult.cs to consume raw query results, applications may need access to HTTP response metadata returned by ClickHouse. Example: X-ClickHouse-Exception-Tag; Content-Encoding (if AutomaticDecompression is set to None); X-ClickHouse-Summary; X-Clickhouse-Timezone; X-Clickhouse-Format

### Describe the solution you'd like
The easy solution: Make 'private readonly HttpResponseMessage response' public,
or provide some other means of exposing the message headers like List> ResponseHeaders.

### Other Considerations
Do something similar in ClickHouseDataReader.cs