Rename Model to IncompressibleModel

[ali-ramadhan]

Note: This PR branches off from #621.

Resolves #566
Resolves #633

[codecov]

Codecov Report

Merging #626 into master will increase coverage by 4.4%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master     #626     +/-   ##
=========================================
+ Coverage   70.47%   74.87%   +4.4%     
=========================================
  Files         118      118             
  Lines        2259     2277     +18     
=========================================
+ Hits         1592     1705    +113     
+ Misses        667      572     -95

Impacted Files	Coverage Δ
src/Utils/launch_config.jl	70.58% <0%> (-29.42%)	⬇️
src/Solvers/pressure_solver.jl	50% <0%> (-2.64%)	⬇️
src/Models/incompressible_model.jl	100% <0%> (ø)	⬆️
src/OutputWriters/checkpointer.jl	90.47% <0%> (+2.38%)	⬆️
...nditions/solution_and_model_boundary_conditions.jl	94.59% <0%> (+5.4%)	⬆️
src/Fields/field.jl	78.68% <0%> (+6.55%)	⬆️
src/Architectures.jl	88.88% <0%> (+22.22%)	⬆️
src/Fields/set!.jl	61.76% <0%> (+26.47%)	⬆️
src/Solvers/plan_transforms.jl	100% <0%> (+33.33%)	⬆️
...c/Solvers/horizontally_periodic_pressure_solver.jl	98.11% <0%> (+56.6%)	⬆️
... and 2 more

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[ali-ramadhan]

@glwagner Was hoping you could review this PR first as #627 (already approved) branches off from this PR.

This PR is partly responsible for why so many files have changed in subsequent PRs (they all branch off from this PR).