When using S3/MinIO backend, the progress callback in AcquireImage was
called synchronously on every 4KB read chunk (via StreamPipe2). Each
call invokes UpdateServerProgress which makes a blocking HTTP PUT to the
compute API (~50ms), capping download speed at ~0.65 Mbps regardless of
available bandwidth.
Fix: throttle the callback to fire at most once every 5 seconds and make
the HTTP call asynchronous (goroutine), matching the behavior of v3.11.x
which used a 1-second ticker with async callbacks.
Fixes#24897
Co-authored-by: Mrliuch <liu15094534492@gmail.com>
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