async bzip2 and add

[adamhathcock]

Related to #992

This pull request adds asynchronous read and write support to the ADC and BZip2 compression streams, enabling non-blocking operations and cancellation support. It introduces new async methods and refactors existing classes to handle asynchronous workflows, improving integration with modern .NET applications. Comprehensive tests are also added to verify the correctness and robustness of the new async features.

ADC Compression/Decompression Enhancements

• Added AdcDecompressResult class to encapsulate results of ADC decompression, including bytes read and output buffer.
• Implemented DecompressAsync methods in ADCBase.cs for asynchronous decompression of byte arrays and streams, supporting cancellation tokens and buffer pooling.
• Added ReadAsync method to ADCStream.cs to support async reading and decompression with cancellation support.

BZip2 Compression/Decompression Enhancements

• Added async read and write methods to BZip2Stream.cs, including overloads for both byte[] and Memory<byte> buffers, supporting cancellation tokens.
• Implemented async read in CBZip2InputStream.cs and async write in CBZip2OutputStream.cs, both with cancellation support. [1] [2]

Test Coverage

• Added AdcAsyncTest.cs to test asynchronous ADC decompression, chunked reads, and cancellation scenarios.
• Added BZip2StreamAsyncTests.cs to verify async compression/decompression, multiple async writes, cancellation, and large data handling for BZip2 streams.

[Copilot]

Pull Request Overview

This PR adds async support to BZip2 and ADC compression streams in SharpCompress. The changes enable asynchronous read and write operations with cancellation token support for improved performance and responsiveness in async-heavy applications.

• Implements ReadAsync and WriteAsync methods for BZip2 and ADC streams
• Adds async-specific unit tests covering compression, decompression, cancellation, and large data scenarios
• Introduces AdcDecompressResult class to encapsulate async decompression results

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 13 comments.

Show a summary per file

File	Description
tests/SharpCompress.Test/Compressors/BZip2/BZip2StreamAsyncTests.cs	New test file with comprehensive async operation tests for BZip2 streams
tests/SharpCompress.Test/AdcAsyncTest.cs	New test file with async operation tests for ADC streams
src/SharpCompress/Compressors/BZip2/CBZip2OutputStream.cs	Implements WriteAsync with cancellation support
src/SharpCompress/Compressors/BZip2/CBZip2InputStream.cs	Implements ReadAsync with cancellation support
src/SharpCompress/Compressors/BZip2/BZip2Stream.cs	Adds async wrapper methods for both array and Memory/Span-based operations
src/SharpCompress/Compressors/ADC/ADCStream.cs	Implements ReadAsync with comprehensive validation and cancellation
src/SharpCompress/Compressors/ADC/ADCBase.cs	Adds DecompressAsync static method and AdcDecompressResult class

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