Add missing tests

[dominichofer]

There's a package but no test for:

• spack info cdo
• spack info eccodes
• spack info eckit
• spack info fckit
• spack info icon-ham
• spack info infero
• spack info libcdi-pio
• spack info libfyaml
• spack info libxml2
• spack info nvidia-blas
• spack info nvidia-lapack
• spack info py-numpy
• spack info py-poetry-core
• spack info py-pytest
• spack info py-setuptools
• spack info py-typing-extensions (but there's a test for py-typing, even though that's not our package 🤷)
• spack info scales-ppm
• spack info yac
• spack info yaxt
• spack spec cdo
• spack spec eccodes
• spack spec icon-ham
• spack spec libcdi-pio
• spack spec libfyaml
• spack spec libxml2
• spack spec nvidia-blas
• spack spec nvidia-lapack
• spack spec py-numpy
• spack spec py-poetry-core
• spack spec py-pytest
• spack spec py-setuptools
• spack spec py-typing-extensions (but there's a test for py-typing, even though that's not our package 🤷)
• spack spec scales-ppm
• spack spec yac
• spack spec yaxt
• system test of ....

[dominichofer]

Implemented with #773