Implicity convert function into FunctionWrappersWrapper

[densmojd]

This PR adds the ability to implicitly convert a function into a FunctionWrappersWrapper. Specific modifications include:

• A FunctionWrappersWrapper outer constructor for when the type parameters are specified and only the function to be wrapped is provided as an argument, i.e., FunctionWrappersWrapper{FW, P, CS}(f). Contrast this function with the existing outer constructor, where all parameters are provided as arguments.
• Specializations of Base.convert for FunctionWrappersWrapper that use the above constructor.

These changes allow composite types with FunctionWrappersWrapper fields to be constructed by providing the functions to be wrapped only. For example, one can construct a Vector{FWW} using:

FWW[sin, cos, log]

for some concrete FWW <: FunctionWrappersWrapper.

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

Closes #52