fix: userSession memory leak - WPB-18909

[netbe]

WPB-18909 [iOS] ZMUserSession is still retained in memory after logout

Issue

This is an attempt to fix some of memory leaks involving userSession.

• add XCUITest to check memory after logout
• add memory label for userSession in DeveloperTools
• remove unused files

Note: this works on an account without activity, but logging out while receiving or having requests ongoing would still be a problem.

Testing

Before fix:

before_fix.mov

** After fix:**
https://github.com/user-attachments/assets/40de0e70-8c91-4b71-8c4a-ccb0e2d6ce2d

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Checklist

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

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UI accessibility checklist

If your PR includes UI changes, please utilize this checklist:

• Make sure you use the API for UI elements that support large fonts.
• All colors are taken from WireDesign.ColorTheme or constructed using WireDesign.BaseColorPalette.
• New UI elements have Accessibility strings for VoiceOver.

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud