core: Reinit longrange stuff on manual cutoff or skin change

[fweik]

Description of changes:

• (d)P3M depends on the local box size and skin (because this sets he bounding box for local particles), so it has to be reinitialized if they change.

@jngrad this is also a candidate for back porting.

[fweik]

Unfortunately I couldn't think of a reliable way to test this in a robust fash, as it depends on loads of other circumstances...

[codecov]

Codecov Report

Merging #3717 into python will increase coverage by 0%.
The diff coverage is 100%.

@@           Coverage Diff            @@
##           python   #3717     +/-   ##
========================================
  Coverage      88%     88%             
========================================
  Files         529     545     +16     
  Lines       23213   24721   +1508     
========================================
+ Hits        20430   21781   +1351     
- Misses       2783    2940    +157     

Impacted Files	Coverage Δ
src/core/event.cpp	94% <100%> (+<1%)	⬆️
src/core/EspressoSystemInterface.hpp	48% <0%> (-22%)	⬇️
src/script_interface/shapes/Torus.hpp	80% <0%> (-20%)	⬇️
src/script_interface/shapes/Rhomboid.hpp	87% <0%> (-13%)	⬇️
src/shapes/include/shapes/Rhomboid.hpp	88% <0%> (-12%)	⬇️
src/script_interface/shapes/Slitpore.hpp	90% <0%> (-10%)	⬇️
src/shapes/include/shapes/Slitpore.hpp	91% <0%> (-9%)	⬇️
src/script_interface/constraints/couplings.hpp	68% <0%> (-6%)	⬇️
src/script_interface/observables/PidObservable.hpp	72% <0%> (-6%)	⬇️
...ipt_interface/observables/PidProfileObservable.hpp	23% <0%> (-5%)	⬇️
... and 252 more

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