[iOS] Switch password details coordinator DCHECK to DWC

crbug.com/40067451 , especially the race condition when a user quickly
navigates to a page, goes back, and re-opens the page again, seems to
have gotten worse on iOS 26. Here, since the PasswordIssuesCoordinator
was only DCHECKing that its PasswordDetailsCoordinator wasn't nil before
creating a new instance, the issue wasn't caught on Stable builds, which
is the channel where most of these race conditions are caught. And
because we we're not crashing on the DCHECK on Stable, we are crashing a
bit later: when a method is called on the zombie coordinator.

Hence, this CL switches the DCHECK to a DumpWithoutCrashing so that the
race condition is caught sooner on Stable and the actual issue is better
reflected in crash reports.

Note: we don't want to actually crash here because of the other scenario
discussed in crbug.com/40067451 , where creating a new coordinator when
the previous one wasn't fully cleaned up isn't a big deal.

Bug: 448355872
Change-Id: Idf875d1641ce35a84d726d811680a7f18080f611
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7003207
Reviewed-by: Tommy Martino <tmartino@chromium.org>
Commit-Queue: Noémie St-Onge <noemies@google.com>
Cr-Commit-Position: refs/heads/main@{#1523767}