Implement separate Fortran and C++ Drivers.

Provide Fortran driver with OpenACC to test portability close to the ICON use-case.

requested review from @k202174

assigned to @k202076

added 2 commits

• 2cd14023 - portability fixes for lumi
• 38e7370c - fix conf.sh for levante

Compare with previous version

mentioned in commit 86f8f6c2

merged