PETSc installed from packages not discovered in Centos 7 full CI builds
On the Centos 7 full CI builds, we're installing PETSc from packages but CMake doesn't find it and PETSc is being built from source as a Nektar++ third party dependency anyway.
This should be resolved by modifying the CMake configuration used to find PETSc to ensure that the package-installed version is discovered. This should also speed up Centos 7 CI full builds.