fix(store/cache): unstick cache metrics names

[walldiss]

Metrics names were not properly delimited. Example:

eds_cacherecent_evicted_counter_total

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 45.07%. Comparing base (2469e7a) to head (d2afb0f).
Report is 347 commits behind head on main.

Files with missing lines	Patch %	Lines
store/cache/metrics.go	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3857      +/-   ##
==========================================
+ Coverage   44.83%   45.07%   +0.24%     
==========================================
  Files         265      314      +49     
  Lines       14620    21801    +7181     
==========================================
+ Hits         6555     9827    +3272     
- Misses       7313    10951    +3638     
- Partials      752     1023     +271     

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