feat: preloads and nodeIntegration in iframes (#16425)

* feat: add support for node / preloads in subframes

This feature has delibrately been built / implemented in such a way
that it has minimum impact on existing apps / code-paths.
Without enabling the new "nodeSupportInSubFrames" option basically none of this
new code will be hit.

The things that I believe need extra scrutiny are:

* Introduction of `event.reply` for IPC events and usage of `event.reply` instead of `event.sender.send()`
* Usage of `node::FreeEnvironment(env)` when the new option is enabled in order to avoid memory leaks.  I have tested this quite a bit and haven't managed to cause a crash but it is still feature flagged behind the "nodeSupportInSubFrames" flag to avoid potential impact.

Closes #10569
Closes #10401
Closes #11868
Closes #12505
Closes #14035

* feat: add support preloads in subframes for sandboxed renderers

* spec: add tests for new nodeSupportInSubFrames option

* spec: fix specs for .reply and ._replyInternal for internal messages

* chore: revert change to use flag instead of environment set size

* chore: clean up subframe impl

* chore: apply suggestions from code review

Co-Authored-By: MarshallOfSound <samuel.r.attard@gmail.com>

* chore: clean up reply usage

* chore: fix TS docs generation

* chore: cleanup after rebase

* chore: rename wrap to add in event fns

docs/api/browser-window.md

@@ -255,6 +255,10 @@ It creates a new `BrowserWindow` with native properties as set by the `options`.
     * `nodeIntegrationInWorker` Boolean (optional) - Whether node integration is
       enabled in web workers. Default is `false`. More about this can be found
       in [Multithreading](../tutorial/multithreading.md).
+    * `nodeIntegrationInSubFrames` Boolean (optional) - Experimental option for
+      enabling NodeJS support in sub-frames such as iframes. All your preloads will load for
+      every iframe, you can use `process.isMainFrame` to determine if you are
+      in the main frame or not.
     * `preload` String (optional) - Specifies a script that will be loaded before other
       scripts run in the page. This script will always have access to node APIs
       no matter whether node integration is turned on or off. The value should