Fix BrotliCompressor.CopyToAsync buffer is not enough

[hadashiA]

#243

BrotoliEncoder.Compress seems to return OperationState.DestinationTooSmall even when the destination buffer is short.

If the length of one BufferSegment is very large (more than the bufferSize parameter), finalState was DestinationTooSmall, the method would complete.
( In #243, MemoryStream is used).

[hadashiA]

Here is the code to reproduce the issue.
#243 (comment)

I have written a slightly shortened version,

const string path1 = "/path/to/test.compressed";

var inputBytes = await File.ReadAllBytesAsync(path1);
System.Console.WriteLine($"Compressed file size (input) : {inputBytes.Length}");

var decompressor = new BrotliDecompressor();
var inputDecompressedBytes = decompressor.Decompress(inputBytes);
System.Console.WriteLine($"Decompressed size (input) : {inputDecompressedBytes.Length}");
var inputDeserialized = MemoryPackSerializer.Deserialize<TradeLog>(inputDecompressedBytes)!;
System.Console.WriteLine($"Decompressed data count (input) : {inputDeserialized.Data.Count}");
decompressor.Dispose();
System.Console.WriteLine("---------------");

var compressor = new BrotliCompressor(CompressionLevel.SmallestSize);
MemoryPackSerializer.Serialize(compressor, inputDeserialized);

// var buffer = new ArrayBufferWriter<byte>(inputBytes.Length);
// compressor.CopyTo(buffer);
var memoryStream = new MemoryStream(inputBytes.Length);
await compressor.CopyToAsync(memoryStream);
memoryStream.Flush();
memoryStream.Seek(0, SeekOrigin.Begin);
// System.Console.WriteLine($"Compressed size (serialized) : {buffer.WrittenSpan.Length}");
System.Console.WriteLine($"Compressed size (serialized) : {memoryStream.Length}");
compressor.Dispose();

var decompressor2 = new BrotliDecompressor();
var decompressedBytes = decompressor.Decompress(memoryStream.ToArray());
System.Console.WriteLine($"Decompressed size (serialized) : {decompressedBytes.Length}");
var deserialized = MemoryPackSerializer.Deserialize<TradeLog>(decompressedBytes)!;
System.Console.WriteLine($"Decompressed data count (serialized) : {deserialized.Data.Count}");
decompressor2.Dispose();

test.compressed data is available from the above comment.

[hadashiA]