Move mpi examples to new runner

[rhodrin]

MPI examples also need moving over.

[codecov]

Codecov Report

Merging #1543 (9ea6958) into master (47a9885) will increase coverage by 2.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1543      +/-   ##
==========================================
+ Coverage   87.31%   89.39%   +2.07%     
==========================================
  Files         206      186      -20     
  Lines       29030    27306    -1724     
  Branches     3915     3703     -212     
==========================================
- Hits        25348    24410     -938     
+ Misses       3243     2449     -794     
- Partials      439      447       +8     

Impacted Files	Coverage Δ
tests/test_gpu_openacc.py	37.34% <0.00%> (-62.66%)	⬇️
examples/seismic/tti/operators.py	62.50% <0.00%> (-33.34%)	⬇️
examples/seismic/elastic/elastic_example.py	47.22% <0.00%> (-30.56%)	⬇️
...mples/seismic/viscoelastic/viscoelastic_example.py	47.22% <0.00%> (-30.56%)	⬇️
tests/test_gpu_openmp.py	73.48% <0.00%> (-25.97%)	⬇️
devito/core/gpu_openacc.py	45.06% <0.00%> (-25.93%)	⬇️
examples/seismic/preset_models.py	34.30% <0.00%> (-24.42%)	⬇️
examples/seismic/tti/tti_example.py	35.13% <0.00%> (-21.63%)	⬇️
examples/seismic/acoustic/acoustic_example.py	30.90% <0.00%> (-20.00%)	⬇️
examples/seismic/tti/wavesolver.py	79.36% <0.00%> (-17.47%)	⬇️
... and 36 more

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