Increase maximum upload chunk to 9MB

[zxcve123]

On embedded system running virtual machines, I observe significant upload performance with higher upload chunk size.

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[github-actions]

Thank you for your contribution @zxcve123! We will review the pull request and get back to you soon.

[azure-sdk]

API change check

API changes are not detected in this pull request.

[antkmsft]

@zxcve123, do you happen to have any performance test for this scenario, so we could see the difference before and after? If not, would it be possible for you to write a piece of code that could demonstrate that?
Also, why 9 - not 8 or 10? How did you find out?

[zxcve123]

@zxcve123, do you happen to have any performance test for this scenario, so we could see the difference before and after? If not, would it be possible for you to write a piece of code that could demonstrate that? Also, why 9 - not 8 or 10? How did you find out?

Upload Results for 16GB in seconds:
Original Performance Test:

           54.47                   53.762                52.855

           Current Performance Test:
           
           43.736                44.327                44.864

The reason i took it 9MB is to allow stream length till 8MB. .we have a check in code at WinHttpRequest::Upload:

// Consider using `MaximumUploadChunkSize` here, after some perf measurements
size_t uploadChunkSize = DefaultUploadChunkSize;
if (streamLength < MaximumUploadChunkSize)
{
  uploadChunkSize = static_cast<size_t>(streamLength);
}

Before this change it defaults to 64KB for anything greater than 1MB.