Remove const char* overload of make_tcp_connector method in net_ip class

[cliffg-softwarelibre]

Currently there is an overload of the make_tcp_connector method in the net_ip class for const char*. This is so that calling make_tcp_connector with two C style strings does not match the make_tcp_connector method that takes a beginning and end iterator. A const char* can be an iterator, and the compiler matches that before doing an implicit conversion and matching the method that takes std::string_view (which is the method that should be matched).

The iterator version of make_tcp_connector can be disabled through std::enable_if matching on const char* (or char*), which then leaves only the std::string_view method as a matching method. This should be implemented to simplify the API.

[cliffg-softwarelibre]

Instead of checking for char* and negating, the std::enable_if checks that the iterator is pointing to an asio::ip::tcp::endpoint and then enables the method, which is a more direct and specific way of implementing the desired functionality.