Rename selected_credential to selected_cipher

[dani-garcia]

📔 Objective

selected_credential is a misleading name as the selected value doesn't have to contain credentials, for example when creating a new passkey a cipher will usually not contain any credentials. Renaming it to selected_cipher should help clear the confusion a bit.

I've left the get_selected_credential function with the same name, as in this case we are actually getting the credential inside the cipher.

⏰ 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 – 85856970-9c90-46c9-bb99-6de731ca0e5d

No New Or Fixed Issues Found

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.

Project coverage is 59.23%. Comparing base (dfd0ba8) to head (e0953ff).

Files	Patch %	Lines
...ates/bitwarden/src/platform/fido2/authenticator.rs	0.00%	6 Missing ⚠️
crates/bitwarden/src/platform/fido2/mod.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #832   +/-   ##
=======================================
  Coverage   59.23%   59.23%           
=======================================
  Files         186      186           
  Lines       12428    12428           
=======================================
  Hits         7362     7362           
  Misses       5066     5066           

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