feat: implement fetch transport (POC)

[hi-ogawa]

Description

base branch: #18362
diff: sapphi-red:refactor/single-transport...hi-ogawa:feat-fetch-transport

On top of #18362 and with a same spirit as #18338, this PR adds a primitives for server and client transports with builtin server middleware. I had initial implementation in hi-ogawa/vite-environment-examples#140 and mostly copied it here. Currently the diff is only the last commit of this PR.

Example (see fetch-transport.spec.ts)

// environment
import { createServerFetchTransport } from "vite"
new DevEnvironment(name, config, {
  hot: true,
  transport: createServerFetchTransport(),
})

// runner
import { createClientFetchTransport } from "vite/module-runner"
const runner = new ModuleRunner(
  {
    root: server.config.root,
    sourcemapInterceptor: false,
    hmr: true,
    transport: createClientFetchTransport('custom', 'http://localhost:5010'),
  },
  new ESModulesEvaluator(),
)

TBD

• it has the same concern as feat: implement fetchable runner #18338 regarding:
  • how to bootstrap runner (e.g. how to pass server url http://localhost:5010, need wait for server listen, etc...),
  • how to protect /@vite/transport request which can expose arbitrary fetchModule