[ISSUE #9885] Fix tiered store cache count and bytes metrics

[majialoong]

Which Issue(s) This PR Fixes

Fixes #9885

Brief Description

Use the correct methods to collect GAUGE_CACHE_COUNT and GAUGE_CACHE_BYTES metrics.

How Did You Test This Change?

unit test

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.31%. Comparing base (63d20eb) to head (4c6c78e).

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #9886      +/-   ##
=============================================
- Coverage      48.39%   48.31%   -0.08%     
+ Complexity     12283    12266      -17     
=============================================
  Files           1314     1314              
  Lines          93903    93905       +2     
  Branches       12046    12046              
=============================================
- Hits           45443    45373      -70     
- Misses         42852    42905      +53     
- Partials        5608     5627      +19     

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