[ISSUE #453] 🚧Add StatsSnapshot struct

[flydream-ylgw]

Which Issue(s) This PR Fixes(Closes)

Fixes #453

Brief Description

How Did You Test This Change?

[codecov]

Codecov Report

Attention: Patch coverage is 94.73684% with 3 lines in your changes missing coverage. Please review.

Project coverage is 22.73%. Comparing base (10c39e5) to head (8c73636).

Files	Patch %	Lines
rocketmq-common/src/common/stats/stats_snapshot.rs	94.73%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #454      +/-   ##
==========================================
+ Coverage   22.46%   22.73%   +0.27%     
==========================================
  Files         217      218       +1     
  Lines       15001    15058      +57     
==========================================
+ Hits         3370     3424      +54     
- Misses      11631    11634       +3     

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