Add new tests and update reference results

[MakisH]

This PR consolidates:

• Adds new system test cases:
  • Add heat-exchanger-simplified to the system tests #731
  • Add perpendicular-flap solid-openfoam and solid-fenics cases to the system tests #746
  • Add flow-over-heated-plate-nearest-projection case to the system tests #747
  • Add Quickstart to the system tests #771
• Reverts a temporary workaround introduced in Enforce recomputation of preconditioner to avoid regression #634:
  • Revert #634 and update reference results #640
• Makes the heat-exchanger-simplified tutorial shorter:
  • Heat exchanger simplified: Reduce max-time and write frequency #770

It also updates the reference results, adding reference results for these cases.