Emptying URLSearchParams causes unwanted "?" char

[stevenvachon]

const url = new URL("http://domain?var=1&var=2&var=3");
const params = Array.from(url.searchParams);

// There is no `.clear()`
for (let param of url.searchParams) {
  url.searchParams.delete( param[0] );
}

console.log(url.href) //-> http://domain/?

url.search = url.searchParams.toString();

console.log(url.href) //-> http://domain/

Tested in Chrome and both correctly log the same (second) value.

[stevenvachon]

@TimothyGu @jasnell

[targos]

Proposed fix: #10486