ODR fixes

[MuAlphaOmegaEpsilon]

When trying to compile the library using CMake unity builds, the compiler errors out due to multiple duplicated function definitions.

This PR removes duplicated code to allow for unity builds to succeed by adhering to the one-definition-rule.

You can try this out with:

$ cmake -B build -DBUILD_TESTS=OFF -DBUILD_EXAMPLES=OFF -DBUILD_PACKAGES=OFF -DBUILD_SHARED_LIBS=OFF -DCMAKE_UNITY_BUILD=ON -DCMAKE_UNITY_BUILD_BATCH_SIZE=100 -DCMAKE_CXX_FLAGS="-DBOOST_NO_CXX11_EXTERN_TEMPLATE"
...
$ cmake --build build

Prior to these changes, the build will break.