Improve volume upload concurrency and progress

[lentitude2tk]

Summary

• move Volume upload options to UploadFilesRequest and reduce default file upload concurrency to 5
• add byte-level upload progress for large files
• make VolumeFileManager upload state request-local so one client instance can run concurrent uploads safely
• keep existing public APIs source-compatible

Tests

• mvn -pl sdk-bulkwriter -DskipTests compile
• mvn -pl sdk-bulkwriter -Dtest=VolumeManagerTest,ProgressInputStreamTest test

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[yhmo]

/lgtm
/approve

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lentitude2tk, yhmo

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