Split networking tests into parts that can be run locally and parts that require a server

The current work-around is to comment out the network-server testing from tests and running individual test-cases.

We currently have a bunch of tests which require a network testing server or the docker setup. But we also have a lot of tests that only use local resources. They're currently sharing the same source-files (e.g. tst_qnetworkreply.cpp), and preferably the tests would be split so that anyone can run the networking tests that only use local resources without needing workarounds. This will let external developers at least run some tests locally, before pushing. Not having to rely on the integration system. They can then also work on and iterate on their own local tests without going through the hoop mentioned at the start or asking for CI pre-checks.

This will break historical data of flaky tests and so on.