Add integration tests for cache behavior, version management, and cross-account access

[reyhankoyun]

Issue #, if available:

Description of changes:
This PR adds new integration tests that validate AWS Secrets Manager Agent behaviors requiring real AWS service interactions.

Changes Made

1. integration-tests/tests/common.rs - Refactoring for targeted setup

• Replaced monolithic setup() with targeted setup methods:
  • setup_basic() - Creates only Basic secrets
  • setup_binary() - Creates only Binary secrets
  • setup_versioned() - Creates only Versioned secrets
  • setup_large() - Creates only Large secrets
• Added created_types field to track which secrets were actually created
• Updated Drop implementation to only delete created secrets
• Updated all test files to use appropriate targeted setup methods
• Removed unused code: setup() method and ALL_SECRET_TYPES constant

Now each test creates only what it needs.

2. integration-tests/tests/cache_behavior.rs - Test optimization and cleanup
3. integration-tests/tests/secret_retrieval.rs - Updated to use targeted setup
4. integration-tests/tests/version_management.rs - Updated to use targeted setup
5. Added documentation at file level for all integ test files

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.72%. Comparing base (2865052) to head (e1873b1).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #145   +/-   ##
=======================================
  Coverage   91.72%   91.72%           
=======================================
  Files          14       14           
  Lines        2418     2418           
  Branches     2418     2418           
=======================================
  Hits         2218     2218           
  Misses        150      150           
  Partials       50       50           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.