Specify C++ standard instead of leaving it up to the compiler

[KoenBussemakerDeltares]

What was done

Instead of using whatever default is set (which differs per compiler and per version), specify the C++ standard in CMake. I chose the C++17 for now but this can be changed if need be.

I also disabled compiler-specific extensions which should lead to fever cross-platform headaches in the future. This causes the linux compile definition to disappear since it's not POSIX compliant, hence why I had to change it to __linux__ in several places.

Evidence of the work done

• Video/figures
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Tests

• Tests updated
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Documentation

• Documentation updated
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Issue link

[harmenwierenga]

FBCTools (src/engines_gpl/fbc/packages/FBCTools/CMakeLists.txt, C++11) and now the new csumo_precice project (src/tools_gpl/csumo_precice/CMakeLists.txt, C++23) override these. It's good to have a decent default though, currently we have the compiler ones (gcc 14 has gnu17 and visual studio 2022 has c++14 I think), and this will apply to dimr.