chore: entry count statistics for cache

[cheb0]

Description

allow to see how many blocks are in the cache right now on dashboards

---

• I have read and followed all requirements in CONTRIBUTING.md;
• I used LLM/AI assistance to make this pull request;

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.62%. Comparing base (2c48a62) to head (fe50952).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #428      +/-   ##
==========================================
- Coverage   70.65%   70.62%   -0.03%     
==========================================
  Files         219      219              
  Lines       17009    17017       +8     
==========================================
+ Hits        12017    12018       +1     
- Misses       4094     4102       +8     
+ Partials      898      897       -1     

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[github-actions]

🔴 Performance Degradation

Some benchmarks have degraded compared to the previous run.
Click on Show table button to see full list of degraded benchmarks.

Show table

Name	Previous	Current	Ratio	Verdict
AggWide/size=1000000-4	2c48a6	324fb8
	467.00 B/op	545.00 B/op	1.17	🔴