Use the Qt5 connection syntax (automated with clazy)

Use the Qt5 connection syntax (automated with clazy)

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.