Stream `KtorDataSource` response body instead of buffering in memory

This change uses `statement.body<HttpResponse>()` instead of
`statement.execute()`. Calling `execute()` without arguments invokes
`fetchResponse()`, which downloads and buffers the entire response body
into memory before returning. Using `body()` invokes
`fetchStreamingResponse()` with `skipSavingBody()`, allowing media
playback to stream directly from the network without OOM errors or
startup delays.

Issue: androidx/media#3305

#cherrypick

PiperOrigin-RevId: 947051534
(cherry picked from commit b308689fcdc5ebfd95212c79dc031a4426bb43f9)