Create cache to optimize.

[hanbings]

Performance can be significantly improved by caching some data:

• This optimization aims to improve performance when traversing a file and need to access the file's Metadata multiple times. Wrap walkdir::DirEntry in a new type #436
• Speed ​​up operations such as getting user and group names from uid and gid.

We should create a centralized cache object and then provide a corresponding interface for the entire program to obtain data.