[ISSUE #6761] Support reentrant notification orderly for broker

[xdkxlk]

Which Issue(s) This PR Fixes

Fixes #6761

Brief Description

How Did You Test This Change?

[codecov-commenter]

Codecov Report

Merging #6762 (58f57d3) into develop (5dc2e20) will decrease coverage by 0.05%.
The diff coverage is 0.00%.

@@              Coverage Diff              @@
##             develop    #6762      +/-   ##
=============================================
- Coverage      42.89%   42.84%   -0.05%     
+ Complexity      9009     8981      -28     
=============================================
  Files           1113     1108       -5     
  Lines          78603    78439     -164     
  Branches       10226    10210      -16     
=============================================
- Hits           33713    33610     -103     
+ Misses         40670    40616      -54     
+ Partials        4220     4213       -7     

Impacted Files	Coverage Δ
...cketmq/broker/processor/NotificationProcessor.java	7.07% <0.00%> (-0.08%)	⬇️
...ing/protocol/header/NotificationRequestHeader.java	0.00% <0.00%> (ø)
.../apache/rocketmq/test/client/rmq/RMQPopClient.java	0.00% <0.00%> (ø)

... and 42 files with indirect coverage changes

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[drpmma]

LGTM