Better error for missing or bad :name arg in make-process etc

Better error for missing or bad :name arg in make-process etc

Improve on the famously bad error message given when the :name keyword
parameter is missing or of the wrong type in calls to make-process,
make-pipe-process and make-network-process (bug#65030).

* src/process.c (get_required_string_keyword_param): New function.
(Fmake_process, Fmake_pipe_process, Fmake_network_process): Use it.