[ISSUE #7904] use string builder to concat string

[ChineseTony]

Which Issue(s) This PR Fixes

Fixes #7904

Brief Description

How Did You Test This Change?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.

Project coverage is 42.95%. Comparing base (db4c7da) to head (d90cd44).
Report is 168 commits behind head on develop.

Files	Patch %	Lines
.../rocketmq/common/namesrv/DefaultTopAddressing.java	0.00%	7 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #7905      +/-   ##
=============================================
+ Coverage      42.92%   42.95%   +0.02%     
- Complexity      9909     9920      +11     
=============================================
  Files           1190     1190              
  Lines          86042    86042              
  Branches       11081    11081              
=============================================
+ Hits           36935    36959      +24     
+ Misses         44531    44521      -10     
+ Partials        4576     4562      -14     

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