#1104 Renamed all five integration tests projects from `*.tests` to `*.tests.integration`

• I did the changes in multiple commits, to make it easier to see what is changed.
• No end-user visible changes.
• Since all integration test plugins are renamed, this will conflict majorly with other merge requests if they change tests or test output. Hence I do this now, as none are open. If you have branches with test changes though, they may need non-trivial merging.

Addresses #1104 (closed)