Changelog: Fix | Feature: Redesign RevisionList for thread-safe, atomic, and distributed revision updates. This resolves critical concurrency issues and enables robust multi-server deployments.
Docs: This PR includes extensive documentation within the codebase: README_REVISIONLIST_REDESIGN.md. A separate PR will be opened in the Conan docs repo.

• Refer to the issue that supports this Pull Request.
  This PR addresses the critical need for thread-safe revision updates with atomic persistence across distributed server instances, preventing data corruption and lost updates.
• If the issue has missing info, explain the purpose/use case/pain/need that covers this Pull Request.
  The current RevisionList implementation suffers from:
  1. Race conditions and lost updates: Due to a lack of internal thread safety and non-atomic read-modify-write operations on disk.
  2. No distributed coordination: File-based locks are insufficient for multi-server deployments.
     This redesign introduces a multi-tier solution:
  • Tier 1 (Essential): Internal threading.RLock for RevisionList and atomic file operations in ServerDiskAdapter to ensure thread-safe, single-server updates.
  • Tier 2 (Recommended): Optimistic locking with version tracking and retry logic for enhanced reliability under high concurrency.
  • Tier 3 (Optional): Redis-based distributed locking for multi-server coordination, with graceful fallback.
• I've read the Contributing guide.
• I've followed the PEP8 style guides for Python code.
• I've opened another PR in the Conan docs repo to the develop branch, documenting this one.