[ISSUE #7622] Revise the measurement method of GROUP_GET_LATENCY to reveal its intended semantics

[RongtongJin]

Which Issue(s) This PR Fixes

Fixes #7622

Brief Description

Revise the measurement method of GROUP_GET_LATENCY to reveal its intended semantics

How Did You Test This Change?

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (06e22b4) 42.93% compared to head (2128d45) 43.01%.

Files	Patch %	Lines
...ocketmq/broker/processor/PeekMessageProcessor.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #7808      +/-   ##
=============================================
+ Coverage      42.93%   43.01%   +0.07%     
- Complexity      9905     9918      +13     
=============================================
  Files           1190     1190              
  Lines          85934    85934              
  Branches       11070    11070              
=============================================
+ Hits           36898    36962      +64     
+ Misses         44476    44393      -83     
- Partials        4560     4579      +19     

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