[iOS][CX] Fix issues with UV in conflict resolution

This CL attempts to fix a bunch of issues with UV:
* Actually sets `_reauthModule` in the credential import coordinator
* Passes the `_reauthModule` instead of re-creating it in the VC
* Simplifies presenting the conflict resolution view - removes the VC
wrapper, and just pushes onto existing navigation controller (the former
actually runs into issues after successful Face ID; the view gets
dismissed somehow)
* Adds a delegate for dismissal of the conflict resolution view, so
Safari coordinator and Credential Import Coordinator can handle the
dismissal in the way that's appropriate for each of them

Fixed: 467635804
Change-Id: I1fd912a36cfcb48d88d8fff1da4032aec702fea8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7251529
Commit-Queue: Rafał Godlewski <rgod@google.com>
Reviewed-by: Tommy Martino <tmartino@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1558264}