Bug 1799996 - Speculative fix checks CFRPopup.anchor is attached to window

We're seeing crashes in the Fenix copy of the `CFRPopup` that are
happening when our activity has already been destroyed, and then we are
trying to add a view to it with the WindowManager.

Our guess from looking at the traces are that the
`BrowserToolbarCFRPresenter` is receiving the `collect call on the main
thread, but further down the event loop. As well as the Runnable in
`CFRPopup#show` that is posting to the end event loop - both of these
calls are putting us in a state where the activity we want has already
been destroyed before we get to the moment where we want to use it.

This is a crash that is difficult to synthesize or write a test for.
As a result, our fix is rather speculative but still straight-forward
and safe to uplift, should it work.

There are three remaining follow-ups to do when fix is confirmed:
1. There is a CFRPopup that was upstreamed which is based on the Fenix
   implementation. We should upstream this patch to that component as
   well.
2. We should remove this copy of the CFRPopup and use the upstreamed
   version to avoid confusion between the two copies.
3. With this change, we are now gracefully failing when our users get
   into this state, however our telemtry and onboarding flows are
   unaware that the CFR was never shown.
   We need to to correct telemetry for `TrackingProtection.tcpCfrShown`
   to stop incorrectly reporting false positives and reset our
   `shouldShowTotalCookieProtectionCFR` pref to false so that we can
   try again at the appropriate time.

Co-authored-by: Christian Sadilek <christian.sadilek@gmail.com>

app/src/main/java/org/mozilla/fenix/compose/cfr/CFRPopup.kt

@@ -72,6 +72,19 @@ class CFRPopup(
      */
     fun show() {
         anchor.post {
+            // When we're in this Runnable, the 'show' method might have been called right before
+            // the activity is no longer attached to the WindowManager. When we get to calling
+            // the CFRPopupFullscreenLayout#show method below, we are now trying to attach the View
+            // with the WindowManager that has an unusable Activity.
+            //
+            // To protect against this, within this same Runnable, we check if the anchor view is
+            // safe to use before continuing.
+            //
+            // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1799996
+            if (anchor.context == null || !anchor.isAttachedToWindow) {
+                return@post
+            }
+
             CFRPopupFullscreenLayout(text, anchor, properties, onDismiss, action).apply {
                 this.show()
                 popup = WeakReference(this)