[IdleTimeout] Adding metrics on ios

This is the extension of crrev.com/c/5186320 for iOS.

The CL records the metrics for idle timeout actions and UI events as follows:

- Time taken to clear browsing data, time taken to sign out and the total time for all actions.
- The success of running of every action and all actions.
- Whether actions run on background or foreground.
- The dialog timeout dialog events (shown, dismissed by user and expired)
- The launch screen events (shown, dismissed on action completion and expired)

Bug: b/301676922
Change-Id: Ib77d33716c6fefb330529cb76060d2c28decdca8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5199432
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Salma Elmahallawy <esalma@google.com>
Cr-Commit-Position: refs/heads/main@{#1248783}