feat: add WebFrameMain detached property (#43473)

* feat: add WebFrameMain detached property

fix: throw instead of returning null senderFrame

test: detached frames

fix: ensure IPCs of pending deletion RFHs are dispatched

fix: lookup WFM by FTN ID to dispatch IPCs

feat: add frame.isDestroyed()

return null

fix: return undefined

docs: add null to all frame properties

refactor: option c, return null and emit warning

refactor: add routingId & processId to navigation events

test: null frame property

docs: clarify warning message

better wording

clarify null frame

fix: browserwindow spec

* maybe fix 🤷

* fix: use updated util #43722

* docs: add notice for frame change of behavior

* docs: clarify why frame properties may be null

* lint

* wip

* fix: content::FrameTreeNodeId lookup and converter

* refactor: avoid holey array deoptimization

---------

Co-authored-by: John Kleinschmidt <jkleinsc@electronjs.org>

spec/fixtures/sub-frames/preload.js

@@ -7,3 +7,7 @@ ipcRenderer.send('preload-ran', window.location.href, webFrame.routingId);
 ipcRenderer.on('preload-ping', () => {
   ipcRenderer.send('preload-pong', webFrame.routingId);
 });
+
+window.addEventListener('unload', () => {
+  ipcRenderer.send('preload-unload', window.location.href);
+});