Add buoyant foam example tests

[hsaunders1904]

Summary

Adds the buoyantFoam examples to our automated test suite.

To run only the buoyantFoam tests:

./run_tests -C test/tests/buoyantFoam

Also in this PR: I've added groups/tags to the test definitions, so it's easier to filter tests when running them.

Checklist

• Tests have been written for the new/changed behaviour.
• Documentation/examples have been added/updated for the new changes.

[hsaunders1904]

Unfortunately, these tests fail. The serial and parallel versions give different results. We expect that the order of the nodes may not be preserved in the parallel version, but we are also seeing different temperatures.

import numpy as np
from netCDF4 import Dataset

ds_serial = Dataset("test/tests/buoyantFoam/buoyantFoam_serial/run_out.e")
ds_par = Dataset("test/tests/buoyantFoam/buoyantFoam_par/run_out.e")

print(ds_serial.variables["vals_nod_var3"][:].max())  # 303.13900450769205
print(ds_par.variables["vals_nod_var3"][:].max())  # 302.38041865733135

# x coordinates are the same, but in different orders
x_serial = ds_serial.variables["coordx"][:]
x_par =  ds_par.variables["coordx"][:]
print(x_serial[0:20])
# [0.         0.01085714 0.02171429 0.03257143 0.04342857 0.05428571
#  0.06514286 0.076      0.         0.01085714 0.02171429 0.03257143
#  0.04342857 0.05428571 0.06514286 0.076      0.         0.01085714
#  0.02171429 0.03257143]
print(x_par[0:20])
# [0.         0.01085714 0.02171429 0.03257143 0.         0.01085714
#  0.02171429 0.03257143 0.         0.01085714 0.02171429 0.03257143
#  0.         0.01085714 0.02171429 0.03257143 0.         0.01085714
#  0.02171429 0.03257143]
print(np.array_equal(np.sort(x_serial), np.sort(x_par)))  # True