[ISSUE #8334] fix: irreducible reference count of mapped file caused by held tiered storage's dispatch

[bxfjb]

Which Issue(s) This PR Fixes

Fixes #8334

Brief Description

How Did You Test This Change?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 45.45455% with 12 lines in your changes missing coverage. Please review.

Project coverage is 43.16%. Comparing base (b31e0ce) to head (c9d68d6).

Files	Patch %	Lines
...q/tieredstore/core/MessageStoreDispatcherImpl.java	40.00%	7 Missing and 5 partials ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #8335      +/-   ##
=============================================
- Coverage      43.19%   43.16%   -0.04%     
+ Complexity     10523    10513      -10     
=============================================
  Files           1274     1274              
  Lines          88940    88945       +5     
  Branches       11434    11435       +1     
=============================================
- Hits           38422    38391      -31     
- Misses         45811    45833      +22     
- Partials        4707     4721      +14     

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