deprecate calcflux -> flux

[ranocha]

I requested a review of @trixi-framework/principal-developers to make them aware of this change and let them add their thoughts here.

Closes #459

[sloede]

LGTM! But I'd like the other @trixi-framework/principal-developers to weigh in as well...

[codecov]

Codecov Report

Merging #463 (c2a2d12) into main (a57a682) will increase coverage by 4.52%.
The diff coverage is 83.65%.

@@            Coverage Diff             @@
##             main     #463      +/-   ##
==========================================
+ Coverage   90.36%   94.88%   +4.52%     
==========================================
  Files         101      101              
  Lines       11235    11353     +118     
==========================================
+ Hits        10152    10772     +620     
+ Misses       1083      581     -502     

Flag	Coverage Δ
unittests	94.88% <83.65%> (+4.52%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/Trixi.jl	100.00% <ø> (ø)
src/equations/lattice_boltzmann_2d.jl	92.98% <0.00%> (+5.84%)	⬆️
src/equations/lattice_boltzmann_3d.jl	91.42% <0.00%> (+6.66%)	⬆️
src/equations/linear_scalar_advection_1d.jl	82.25% <0.00%> (+1.61%)	⬆️
src/equations/linear_scalar_advection_2d.jl	81.48% <0.00%> (+3.70%)	⬆️
src/equations/linear_scalar_advection_3d.jl	82.69% <0.00%> (+5.76%)	⬆️
src/equations/acoustic_perturbation_2d.jl	92.53% <66.66%> (+5.97%)	⬆️
.../equations/compressible_euler_multicomponent_2d.jl	97.55% <66.66%> (+1.50%)	⬆️
src/equations/equations.jl	84.37% <66.66%> (+1.04%)	⬆️
src/equations/hyperbolic_diffusion_1d.jl	86.41% <66.66%> (+3.70%)	⬆️
... and 106 more

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[gregorgassner]

I like the change from calc flux to flux!