Remove depandancie build from CMake

[vancraar]

Since we propose a DisCoTec spack package (https://raw.githubusercontent.com/freifrauvonbleifrei/spack/develop/var/spack/repos/builtin/packages/discotec/package.py), would it probably be a better idea to build the dependencies cleanly over spack and not have it redundantly in CMake.

Some alternatives for building DisCoTec with spack:

• get the spack package:

  wget https://raw.githubusercontent.com/freifrauvonbleifrei/spack/develop/var/spack/repos/builtin/packages/discotec/package.py -O $SPACK_ROOT/repos/builtin/packages/discotec/package.py

• Variant 0: direct install with spack:

  spack install discotec

• Variant 1: install DisCoTec and load dependencies:

  spack install -y discotec@main%gcc@9.4.0
  spack load --only dependencies discotec@main%gcc@9.4.0

• Variant 2: spack dev-build

  git clone git@github.com:SGpp/DisCoTec.git discotec
  cd discotec
  spack dev-build discotec@master

• Variant 3: spack develop:

  mkdir dev-folder
  cd dev-folder
  spack env create -d .  
  spack add discotec
  spack develop discotec@main 
  spack install

• Variant 4: just building the dependencies by hand/with spack

[vancraar]

As discussed, it makes more sense to make the HAVE_HIGHFIVE flag unique for DisCoTec and set it PUBLIC. This is implemented in the last commit with DISCOTEC_USE_HIGHFIVE.