Implement ClickHouseRawResult cancellation APIs

[Skyuzii]

Summary

Fixes #546

Implement ClickHouseRawResult cancellation APIs

Warning: A test for passing a cancelled token to ReadAsStreamAsync was not added, as it is ignored in .NET. - Link

Checklist

Delete items not relevant to your PR:

• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided to include in CHANGELOG

[Copilot]

Pull request overview

This PR adds cancellation-token overloads to ClickHouseRawResult read/copy APIs so callers can cancel ReadAsStringAsync, ReadAsByteArrayAsync, stream reads, decompressed-stream reads, and CopyToAsync, aligning the raw-result surface with typical .NET async cancellation patterns.

Changes:

• Added CancellationToken overloads for ReadAsStreamAsync, ReadDecompressedStreamAsync, ReadAsByteArrayAsync, ReadAsStringAsync, and CopyToAsync on ClickHouseRawResult.
• Expanded ADO test coverage to validate the new overloads and canceled-token behavior for buffering/copying operations.
• Added a changelog fragment for issue #546.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
ClickHouse.Driver/ADO/Readers/ClickHouseRawResult.cs	Adds cancellation-token overloads for raw result reading/copying APIs.
ClickHouse.Driver.Tests/ADO/RawResultReaderAsyncTests.cs	Adds/renames tests to cover new cancellation overloads and cancellation behavior.
ClickHouse.Driver.Tests/ADO/ClickHouseRawResultDecompressionTests.cs	Adds cancellation-related tests for decompressed stream reads.
changelog.d/546-raw-result-reader-cancellation-api.improvements.md	Changelog fragment documenting the user-facing improvement.

Suppressed comments (1)

ClickHouse.Driver/ADO/Readers/ClickHouseRawResult.cs:130

• ReadDecompressedStreamAsync(CancellationToken) currently relies on HttpContent.ReadAsStreamAsync(cancellationToken) for cancellation. If that underlying overload ignores cancellation, this method won’t honor an already-canceled token (and the added test that expects OperationCanceledException becomes unreliable). Add an explicit pre-check before acquiring/wrapping the content stream.

        if (decompressedStream != null)
            return decompressedStream;

        var rawStream = await response.Content.ReadAsStreamAsync(cancellationToken).ConfigureAwait(false);

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