Faster String arguments

With research & benchmarks done by @BV-WebDev, this release introduces optimizations for methods taking JavaScript Strings. The following demo runs with 17% higher req/sec overall, entirely due to this faster String argument passing:

get('/', (res, req) => {
  res.writeHeader("Hello", "There");
  res.writeHeader("Hi", "On you");
  res.end('Hello World!');
})

This optimization applies to Node.js 24 or later and relies on the new v8::String::ValueView.