fix: Unable to tab to Contacts - WPB-10514

[github-actions]

WPB-10514 [iOS] Difficulty with contacts screen

This PR was automatically cherry-picked based on the following PR:

• fix: Unable to tab to Contacts - WPB-10514 #1829

Original PR description:

---

Issue

This PR fixes an unreleased bug that prevents showing the contacts view when the navigation is in a certain state. For example the following would occur prior to this fix 100% of the time:

1. Quit app
2. Launch app
3. Tap Folders
4. Tap Contacts
5. Tap close on contacts
6. Tap Contacts - Nothing happens no matter how many times the user taps Contacts.

The root cause of the issue is that currently ConversationListViewController is the delegate of the UITabBarController and we have two instances of ConversationListViewController - used for Conversations & Folders tabs - which both set themselves as the delegate of UITabBarController and respond to taps on the Contacts & Archive tabs by presenting a corresponding view controller on self - i.e whichever ConversationListViewController instance is the true delegate of UITabBarController. This can lead to some messed up state.

The above is necessary because how we are currently (maybe) misusing our UITabBarController - Two tabs (Conversations & Folders) contain ConversationListViewController instances with real content. The other two tabs (Contacts & Archive) contain empty UIViewController instances. We use these empty tabs as buttons and have the UITabBarControllerDelegate perform actions depending on which tab is selected.

To address this issue, this PR introduces TabBarChangeHandler which becomes the single delegate of the main UITabBarController instance. It tracks the currently selected real content tab (i.e Conversations or Folders) and makes sure to present content for Contacts & Archive on the correct real content tab.

The solution is not pretty but seems to work and is temporary. This work will all be discarded in our ongoing navigation overhaul #1361. I have attempted to minimize changes to avoid conflicts with #1361.

Testing

1. Quit app
2. Launch app
3. Tap Folders
4. Tap Contacts
5. Tap close on contacts
6. Tap Contacts - This should work
7. Keep tapping on all tabs trying to break things.

Checklist

• Title contains a reference JIRA issue number like [WPB-XXX].
• Description is filled and free of optional paragraphs.
• Adds/updates automated tests.

[github-actions]

Test Results

    2 files    302 suites   2m 39s ⏱️
1 854 tests 1 854 ✅ 0 💤 0 ❌
1 862 runs  1 862 ✅ 0 💤 0 ❌

Results for commit 1d4a6a3.

♻️ This comment has been updated with latest results.

[datadog-wireapp]

Datadog Report

Branch report: fix/tapping-contacts-tab-WPB-10514-cherry-pick
Commit report: 69c4db5
Test service: wire-ios-mono

✅ 0 Failed, 1854 Passed, 0 Skipped, 13.84s Total Time
❄️ 1 New Flaky

New Flaky Tests (1)

• test_it_refreshes_if_timeout_expired - Wire_iOS_Tests.TeamMetadataRefresherTests - Last Failure

  Expand for error

   Asynchronous wait failed: Exceeded timeout of 2 seconds, with unfulfilled expectations: "triggered second refresh".
   
   wire-ios/Wire-iOS Tests/TeamMetadataRefresherTests.swift:103