Temporary mitigation to run terminateIncognitoSession after init.

If incog tabs are closed before initialization it would finish the
activity. This worked well for some call sites, but others this would
make the browser unusable, shutting down on start up. This problem is
mitigated by just waiting for init to complete.

This has a significant downside that we now have a temporary state where
all the incognito tabs still load. And observers waiting for tab model
init may see them before our observer is run. So only use the new
closeAllIncognitoTabsOnInit version from supervised user call site.

Bug: 429478269
Change-Id: I7b10352078886a0c5c13471f5fabcc03ef2eaf08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6764578
Reviewed-by: Tomek Jurkiewicz <tju@google.com>
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Commit-Queue: Sky Malice <skym@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1488326}