refactor(cache): move to x

[flc1125]

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[what-the-diff]

PR Summary

• Gitignore File Update
  The .gitignore file, which helps control which files get tracked by our version control system, was updated to exclude a _backup directory. This means that files in the _backup directory will be ignored and stay untracked providing a cleaner working environment.

• Deletion of Old System Cache Files
  Several related files were removed from the cache directory including manager.go, manager_test.go, redis/store.go, redis/store_test.go, repository.go, repository_test.go, and util.go. These files previously served to manage the cache of our system, helping it retrieve data faster.

• Structure Refinement & New Directories
  A new directory named x was established. This directory also contains a simple README.md file that would typically hold information about the directory, and a subdirectory, x/cache.

• Introduction of New Cache System
  Within the new x/cache directory, a few files were added: redis/store.go, redis/store_test.go, repository.go. These files represent a new approach to our caching system, effectively replacing the old system that was removed.

• File Renaming for Better Organization
  A file previously named contract/cache/store.go was renamed and moved into the new directory structure for better terminology consistency and organization. It is now located at x/cache/store.go.