[NO-JIRA] Refactor integration tests module

[SimonBaars]

I recently picked up a task to remove the forkMode parameter (#575), and found parts of the code hard to work with because of redundant constructs in the code:

• When a method has throws Exception, I expect the method to throw the wildest things if we have to use the base Exception class in the method declaration. Oftentimes, there were no checked exceptions at all. I removed the declarations where they were not needed and refactored some others where Exception was too much to be thrown.
• There was some commented code dating back many years ago, which is unlikely to be used again. Better to remove it and reduce cognitive load.
• Some methods were unused.
• A few other small issues

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[slawekjaranowski]

@SimonBaars can you resolve conflicts?

[SimonBaars]

@SimonBaars can you resolve conflicts?

On it!

[slawekjaranowski]

@SimonBaars thanks