…tron#51923)

* chore: remove EnvironmentOptions::experimental_fetch dependency

Node.js removed the experimental_fetch option in nodejs/node#62759
since fetch is now unconditionally enabled. We had been patching the
field back in so that node_main.cc could read it and node_bindings.cc
could pass --no-experimental-fetch to renderer/worker processes.

Neither is necessary:

- In ELECTRON_RUN_AS_NODE mode, fetch is always available, so WASM
  streaming (which depends on Response) should always be set up.
- In renderer/worker processes, kNoBrowserGlobals already causes
  Node's PrincipalRealm::BootstrapRealm to skip
  internal/bootstrap/web/exposed-window-or-worker.js, which is where
  fetch/Request/Response/Headers/FormData are defined. Node's fetch
  globals were never being installed; Blink's win by default.

Drop the patch and the two call sites that depended on it.

Closes electron#51912

* fix: restore Blink's WASM streaming callback in renderer/worker

SetIsolateUpForNode now unconditionally registers Node's WASM streaming
callback (nodejs/node#62759 dropped the experimental_fetch gate). With
kNoBrowserGlobals the JS half of that callback is never installed, so
WebAssembly.compileStreaming/instantiateStreaming would crash on
CHECK(\!impl.IsEmpty()) in node_wasm_web_api.cc.

Re-register Blink's handler via WasmResponseExtensions::Initialize after
CreateEnvironment in renderer and worker so Blink's implementation wins.

Also drop the now-redundant blink* global stash/restore: with
kNoBrowserGlobals Node neither installs nor deletes fetch/Response/etc,
so Blink's bindings are never disturbed and the round-trip through
blinkfetch was a no-op.

Add a spec asserting fetch/Headers/Request/Response/FormData stringify
to [native code] in a nodeIntegration renderer.

* fixup: rebase on electron#51953 and preserve Blink's EventSource

- Resolve modify/delete on the fetch patch (delete wins; the
  experimental_fetch gate it added to environment.cc is no longer
  needed since WasmResponseExtensions::Initialize handles the
  callback restoration in Electron's renderer code).
- Revert the environment.cc index hash in
  api_delete_deprecated_fields_on_v8_isolate.patch now that the
  preceding patch is gone (verified with `e patches node`).
- Preserve Blink's EventSource around LoadEnvironment in renderer
  and worker: Node's setupEventsource() in pre_execution.js deletes
  globalThis.EventSource whenever --experimental-eventsource is not
  set, and unlike setupNavigator/setupWebStorage it does not check
  noBrowserGlobals first. The previous blink* stash covered this as
  a side effect; restore just EventSource explicitly in C++.
- Extend the [native code] spec assertion to cover EventSource.

* fixup: pass --experimental-eventsource instead of C++ save/restore

The C++ save/restore around LoadEnvironment was too late: preload
scripts run inside LoadEnvironment, after Node's setupEventsource()
has deleted globalThis.EventSource but before the C++ restore. This
broke 'preload has synchronous access to all eventual window APIs'.

Pass --experimental-eventsource for renderer/worker so Node's
setupEventsource() becomes a no-op and Blink's binding is never
deleted. Under kNoBrowserGlobals Node never installs its own undici
EventSource, so the flag's only effect is suppressing the delete.