[ISSUE #9544] Must correct file size when init the file segment

[lizhimins]

Which Issue(s) This PR Fixes

Fixes #9544

Brief Description

How Did You Test This Change?

[codecov-commenter]

Codecov Report

❌ Patch coverage is 42.85714% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.03%. Comparing base (76cee72) to head (197b314).
⚠️ Report is 9 commits behind head on develop.

Files with missing lines	Patch %	Lines
...ache/rocketmq/tieredstore/file/FlatAppendFile.java	42.85%	7 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #9545   +/-   ##
==========================================
  Coverage      48.02%   48.03%           
- Complexity     12039    12046    +7     
==========================================
  Files           1313     1313           
  Lines          92762    92771    +9     
  Branches       11862    11862           
==========================================
+ Hits           44547    44559   +12     
- Misses         42695    42698    +3     
+ Partials        5520     5514    -6     

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[lollipopjin]

LGTM