Do some refactor for naming notify event.

[KomachiSion]

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What is the purpose of the change

For #10374

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Verifying this change

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 93.93939% with 4 lines in your changes missing coverage. Please review.

Project coverage is 68.80%. Comparing base (7cdf224) to head (92257b2).
Report is 67 commits behind head on develop.

Files	Patch %	Lines
...a/nacos/client/naming/backups/FailoverReactor.java	57.14%	1 Missing and 2 partials ⚠️
...libaba/nacos/client/naming/NacosNamingService.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop   #12167      +/-   ##
=============================================
+ Coverage      68.78%   68.80%   +0.02%     
- Complexity      9221     9229       +8     
=============================================
  Files           1263     1264       +1     
  Lines          41177    41183       +6     
  Branches        4360     4361       +1     
=============================================
+ Hits           28322    28336      +14     
+ Misses         10815    10810       -5     
+ Partials        2040     2037       -3     

Files	Coverage Δ
...aba/nacos/client/naming/cache/InstancesDiffer.java	100.00% <100.00%> (ø)
...a/nacos/client/naming/cache/ServiceInfoHolder.java	93.84% <100.00%> (+2.54%)	⬆️
...acos/client/naming/event/InstancesChangeEvent.java	100.00% <ø> (ø)
.../client/naming/selector/NamingListenerInvoker.java	77.77% <100.00%> (+6.34%)	⬆️
...libaba/nacos/client/naming/NacosNamingService.java	88.32% <0.00%> (-0.46%)	⬇️
...a/nacos/client/naming/backups/FailoverReactor.java	69.47% <57.14%> (-3.94%)	⬇️

... and 2 files with indirect coverage changes

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