Removed ghost flag globals

[fweik]

Description of changes:

• Calculate required ghost data parts on the fly.
• Reorganized some of the cell update code to make data
  parts passable as an argument.
• Optimized some of the ghost flags.

[codecov]

Codecov Report

Merging #3399 into python will increase coverage by <1%.
The diff coverage is 93%.

@@           Coverage Diff           @@
##           python   #3399    +/-   ##
=======================================
+ Coverage      86%     86%   +<1%     
=======================================
  Files         538     538            
  Lines       25233   25282    +49     
=======================================
+ Hits        21755   21804    +49     
  Misses       3478    3478

Impacted Files	Coverage Δ
src/core/communication.hpp	100% <ø> (ø)	⬆️
src/core/shapes/Torus.hpp	80% <ø> (ø)	⬆️
src/core/cells.hpp	100% <ø> (ø)	⬆️
src/core/particle_data.hpp	100% <ø> (ø)	⬆️
src/core/statistics.hpp	87% <ø> (ø)	⬆️
src/core/ghosts.hpp	100% <ø> (ø)	⬆️
...re/electrostatics_magnetostatics/p3m_send_mesh.cpp	100% <ø> (ø)	⬆️
...re/electrostatics_magnetostatics/p3m_send_mesh.hpp	100% <ø> (ø)	⬆️
src/core/energy_inline.hpp	67% <ø> (ø)	⬆️
src/core/global.cpp	83% <ø> (ø)	⬆️
... and 46 more

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