Previously the job would only become "active" when the downloads
started. That meant that arbitrarily many hash computations could be
queued at the same time.
Since the the file was opened during future creation this could lead to
a "too many open files" problem if there were lots of new-new conflicts.
To change this:
- Make PropagateDownload become active when computing a hash
asynchronously.
- Make the computation future open the file only once it gets run. This
will make it less likely for this problem to occur even if thousands
of these futures are queued.
For #7372
This is motivated by the fact that QMetaObject::noralizeSignature takes 7.35%
CPU of the LargeSyncBench. (Mostly from ABstractNetworkJob::setupConnections and
PropagateUploadFileV1::startNextChunk). It could be fixed by using normalized
signature in the connection statement, but i tought it was a good oportunity
to modernize the code.
This commit only contains calls that were automatically converted with clazy.
