module: change default resolver to not throw on unknown scheme

[giltayar]

This is an example toy loader that supports HTTP[S]. This code should work (in a simplistic way):

export async function load(url, context, nextLoad) {
  if (url.startsWith('http://') || url.startsWith('https://')) {
    const response = await fetch(url, {redirect: 'follow'})
    const source = await response.text()

    return {shortCircuit: true, format: 'module',source}
  }
  return await nextLoad(url, context)
}

Unfortunately, this won't work. If you use it, you will get an ERR_UNSUPPORTED_ESM_URL_SCHEME because the default Node.js resolver doesn't support HTTPS, and throws on unknown schemes. So unfortunately I had to write that this loader needs a resolver, even though the only thing it does is support loading HTTPS. And the resolver I had to wrote was non-trivial, and IIUC replicates some of what the default resolver does:

export async function resolve(specifier, context, nextResolve) {
  if (isBareSpecifier(specifier))
    return await nextResolve(specifier, context)

  const url = new URL(specifier, context.parentURL).href

  if (url.startsWith('http://') || url.startsWith('https://'))
    return {url, shortCircuit: true}

  return await nextResolve(specifier, context)
}

Thinking about it more, I realized that the only reason I need to write this resolver is that Node.js doesn't recognize the HTTP scheme in its resolver. But if Node.js would have not recognized the scheme in the loader, then I wouldn't have needed to write this resolver at all.

So my point is this: both checks for unknown scheme and unknown file extension should move from the default Node.js resolver to the default Node.js loader. This will obviate the need for some loaders to implement a resolve which mostly replicates the Node.js logic, just for the sake of avoiding these exceptions.

This PR implements exactly that.

Fixes nodejs/loaders#138

Notable change:

The ESM loader no longer throws on unknown protocol/file extension in the resolve phase, so import.meta.resolve behavior matches the behavior of other runtimes. This change is potentially for loader hooks authors that rely on the old behavior.