Test cleanup

[TorkelE]

I went through the tests, trying to see if there is anything that can be cut. Most of it is complication time, however, I found some Jump simulations across two files where I could remove some probably superfluous repeats of the simulations. It only removed like 1 minute in the end, had hoped to gain more.

While I went through stuff I removed some unnecessary statements, and only added a few missing StableRNG uses (where rand was called without StableRNG input).

[isaacsas]

To be honest at some point we should probably update the jump solution tests to use examples with known solutions / solution statistics as in JumpProcesses, and compare to those. All these ones you are modifying are not such great accuracy tests.