Fix GH-10031: [Stream] STREAM_NOTIFY_PROGRESS over HTTP emitted irregularly for last chunk of data

It's possible that the server already sent in more data than just the headers.
Since th

Fix GH-10031: [Stream] STREAM_NOTIFY_PROGRESS over HTTP emitted irregularly for last chunk of data

It's possible that the server already sent in more data than just the headers.
Since the stream only accepts progress increments after the headers are
processed, the already read data is never added to the process.
We account for this by adjusting the progress counter by the difference of
already read header data and the body.

For the test:
Co-authored-by: aetonsi <18366087+aetonsi@users.noreply.github.com>

Closes GH-10492.

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