Remove explicit template instantiations (#32)

I know of no reason why explicit template instantiations should ever
appear in a header file: code that includes the header file will
already implicitly instantiate any templates that it uses. The effect
of the instantiations is only to copy unnecessary object code into
every translation unit that calls this library.

In any case, for trivial wrapper structs it's always better to use
function inlining anyway; for performance, we don't actually want to
be jumping through extern functions when dealing with these wrappers.

include/cpp/DefaultInfo.h

@@ -30,8 +30,4 @@ struct DefaultInfo
     clarabel::SolverStatus status;
 };
 
-// Instantiate the templates
-template struct DefaultInfo<double>;
-template struct DefaultInfo<float>;
-
 } // namespace clarabel

include/cpp/DefaultSettings.h

@@ -59,10 +59,6 @@ struct DefaultSettings
     static DefaultSettings<T> default_settings();
 };
 
-// Instantiate the templates
-template struct DefaultSettings<double>;
-template struct DefaultSettings<float>;
-
 template<typename T = double>
 class DefaultSettingsBuilder
 {

include/cpp/DefaultSolution.h

@@ -67,8 +67,4 @@ class DefaultSolution
     }
 };
 
-// Instantiate the templates
-template struct DefaultSolution<double>;
-template struct DefaultSolution<float>;
-
 } // namespace clarabel