GridapGeosciences Parallelization

[amartinhuertas]

This is working in progress, thus I open the PR in draft mode so that we may start familarizing with the work I am doing, discuss whatever is needed, etc.

The final goal of this PR is introduce the MPI-parallel version of GridapGeosciences.jl. Some overarching goals are:

• Maximize reuse of code among the sequential and parallel codes (this is possible as the high-level API of Gridap and GridapDistributed match).
• Separate among sequential and parallel codes wherever appropiate (e.g., CubedSphereDiscreteModel versus p4est-based CubedSphereDistributedDiscreteModel). To this end, we try to separate the src and test source directories into sequential and mpi subdirectories.

This PR introduces a bunch of new major packages which are required to support distributed-memory parallelization, namely:

• MPI.jl - Julia wrappers for MPI.
• PartitionedArrays.jl - Julia native distributed linear algebra and communication layer.
• GridapPETSc.jl - Gridap/GridapDistributed wrappers for PETSc.jl written in Julia.
• GridapP4est.jl - Gridap wrappers for p4est written in Julia.
• GridapDistributed.jl - Parallel finite element library.

[Solved] Some of these are still under active development, with yet unreleased ongoing versions, so that we may have to point to these via the Manifest.toml file as usual.

[codecov-commenter]

Codecov Report

Merging #26 (034a430) into master (d1c7b26) will not change coverage. The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master     #26    +/-   ##
=======================================
  Coverage    0.00%   0.00%            
=======================================
  Files          17      18     +1     
  Lines        1056    1258   +202     
=======================================
- Misses       1056    1258   +202     

Impacted Files	Coverage Δ
src/DiagnosticTools.jl	0.00% <0.00%> (ø)
src/Helpers.jl	0.00% <0.00%> (ø)
src/ShallowWaterExplicit.jl	0.00% <0.00%> (ø)
src/ShallowWaterIMEX.jl	0.00% <0.00%> (ø)
src/ShallowWaterRosenbrock.jl	0.00% <0.00%> (ø)
src/ShallowWaterThetaMethodFullNewton.jl	0.00% <0.00%> (ø)
src/ThermalShallowWaterExplicit.jl	0.00% <0.00%> (ø)
src/mpi/CubedSphereDistributedDiscreteModels.jl	0.00% <0.00%> (ø)

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[amartinhuertas]

Some of these are still under active development, with yet unreleased ongoing versions, so that we may have to point to these via the Manifest.toml file as usual.

This has been fixed in 02630c7. Let us see if the tests pass.

[amartinhuertas]

Ok, tests are passing now! :muscle: Accepting PR !