[PM-17628] Move all files from libs/importer/spec into libs/importer/src

[djsmith85]

🎟️ Tracking

https://bitwarden.atlassian.net/browse/PM-17628

📔 Objective

This PR moves all files from libs/importer/spec into libs/importer/src in preparation to separate libs/importer into libs/importer-core and libs/importer-ui packages
Renamed test-data dir to spec-data dir

⏰ 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 – 8f4dde5b-0274-4cad-ad45-cb86ddf484f4

Great job, no security vulnerabilities found in this Pull Request

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 35.55%. Comparing base (1d71212) to head (883b918).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13202      +/-   ##
==========================================
+ Coverage   35.48%   35.55%   +0.06%     
==========================================
  Files        3007     3100      +93     
  Lines       90899    90996      +97     
  Branches    16908    16908              
==========================================
+ Hits        32260    32354      +94     
- Misses      56137    56140       +3     
  Partials     2502     2502              

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