Add testing and checks to all `fenics-*` Spack packages

[jhale]

Describe new/missing feature

Spack supports build time tests, install sanity checking and standalone (quick) tests of packages which would help end users ensure that what Spack builds is actually OK.

https://spack.readthedocs.io/en/latest/packaging_guide_testing.html

In some cases, tests can be discovered through standard hooks, e.g. make check and make test which was implemented for DOLFINx C++ in #3858, but the other packages e.g. packages using pytest will require some custom work.

[jorgensd]

Describe new/missing feature

Spack supports build time tests, install sanity checking and standalone (quick) tests of packages which would help end users ensure that what Spack builds is actually OK.

https://spack.readthedocs.io/en/latest/packaging_guide_testing.html

In some cases, tests can be discovered through standard hooks, e.g. make check and make test which was implemented for DOLFINx C++ in #3858, but the other packages e.g. packages using pytest will require some custom work.

Note that the python testing in spack is quite broken: spack/spack#45801
Not even import tests do as they should.

[jhale]

Thanks good to know, and surprising that such an important feature is broken - I guess we will have to limit ourselves to DOLFINx C++ for the time being then.