src: reduce to simple `const char*` in OptionsParser

> A lot of the `std::string` usage here could be reduced
  to simple `const char*`s if it's reasonable to expect the values to be
  known at compile-time.

So this commit uses `const char*` to replace most of `std::string` in
`OptionsParser`.

PR-URL: https://github.com/nodejs/node/pull/26297


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Beth Griggs <Bethany.Griggs@uk.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>