[FEA] Replace internal usage of std::string with std::string_view

**Is your feature request related to a problem? Please describe.**
There are currently a number of libcudf functions that accept a std::string argument when they don't need to own the string but could simply use a view. Others take a const ref to a std::string, explicitly indicating that they don't require ownership. These include:
- https://github.com/rapidsai/cudf/blob/ce247961216dd70f389763dc086f137c11ad7346/cpp/include/cudf/aggregation.hpp#L559
- https://github.com/rapidsai/cudf/blob/ce247961216dd70f389763dc086f137c11ad7346/cpp/include/cudf/interop.hpp#L107
- https://github.com/rapidsai/cudf/blob/ce247961216dd70f389763dc086f137c11ad7346/cpp/include/cudf/io/types.hpp#L210 (multiple in this file)
- https://github.com/rapidsai/cudf/blob/ce247961216dd70f389763dc086f137c11ad7346/cpp/include/cudf/io/json.hpp#L386 (multiple in this file, and also all other I/O format files like csv.hpp)

There may be others as well.

**Describe the solution you'd like**
We should do a thorough audit of std::string usage in libcudf to ensure that we are properly using std::string_view instead where appropriate.

**Additional context**
A subset of this request was originally documented in https://github.com/rapidsai/cudf/issues/14413, which indicates that some of these changes may be nontrivial to implement.