[PM-23300] Store session values to keychain so they can be shared between app and autofill

[KatherineInCode]

🎟️ Tracking

https://bitwarden.atlassian.net/browse/PM-23300

📔 Objective

⚠️ This is still very much a draft of work in progress ⚠️

This moves the storage of several values related to session length from UserDefaults to the shared keychain. This allows the app and the autofill extension (and other extensions) to share these values, which allows things like session timeout to be shared between both of them. As well, this makes these values more secure.

⏰ Reminders before review

• Contributor guidelines followed
• All formatters and local linters executed and passed
• Written new unit and / or integration tests where applicable
• Protected functional changes with optionality (feature flags)
• Used internationalization (i18n) for all UI strings
• CI builds passed
• Communicated to DevOps any deployment requirements
• Updated any necessary documentation (Confluence, contributing docs) or informed the documentation team

🦮 Reviewer guidelines

• 👍 (:+1:) or similar for great changes
• 📝 (:memo:) or ℹ️ (:information_source:) for notes or general info
• ❓ (:question:) for questions
• 🤔 (:thinking:) or 💭 (:thought_balloon:) for more open inquiry that's not quite a confirmed issue and could potentially benefit from discussion
• 🎨 (:art:) for suggestions / improvements
• ❌ (:x:) or ⚠️ (:warning:) for more significant problems or concerns needing attention
• 🌱 (:seedling:) or ♻️ (:recycle:) for future improvements or indications of technical debt
• ⛏ (:pick:) for minor or nitpick changes

[github-actions]

Checkmarx One – Scan Summary & Details – 111a3361-f390-4189-a3ea-012b229d6721

Great job! No new security vulnerabilities introduced in this pull request

[codecov]

Codecov Report

❌ Patch coverage is 91.88791% with 55 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.81%. Comparing base (9a806a2) to head (8dee6ca).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
.../Services/TestHelpers/MockKeychainRepository.swift	29.41%	24 Missing ⚠️
...Shared/Core/Auth/Services/KeychainRepository.swift	70.49%	18 Missing ⚠️
...re/Platform/Services/UserSessionStateService.swift	71.42%	6 Missing ⚠️
...Services/KeychainRepository+UserSessionTests.swift	96.50%	5 Missing ⚠️
...enShared/Core/Platform/Services/StateService.swift	95.12%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2239      +/-   ##
==========================================
+ Coverage   85.65%   85.81%   +0.15%     
==========================================
  Files        1758     1763       +5     
  Lines      149452   150878    +1426     
==========================================
+ Hits       128009   129470    +1461     
+ Misses      21443    21408      -35     

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