Revert "optimize: the high CPU usage issue of the rpcMergeMessageSend thread (#6061)

[funky-eyes]

• I have registered the PR changes.

Ⅰ. Describe what this PR did

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov]

Codecov Report

Merging #6163 (5f8505d) into 2.x (5563492) will increase coverage by 0.00%.
The diff coverage is 45.83%.

Additional details and impacted files

@@            Coverage Diff            @@
##                2.x    #6163   +/-   ##
=========================================
  Coverage     48.94%   48.95%           
- Complexity     4775     4776    +1     
=========================================
  Files           913      913           
  Lines         31710    31697   -13     
  Branches       3827     3823    -4     
=========================================
- Hits          15521    15517    -4     
+ Misses        14653    14638   -15     
- Partials       1536     1542    +6     

Files	Coverage Δ
...io/seata/core/rpc/netty/AbstractNettyRemoting.java	14.28% <100.00%> (ø)
...ta/core/rpc/netty/AbstractNettyRemotingClient.java	18.71% <43.47%> (+0.20%)	⬆️

... and 6 files with indirect coverage changes

[slievrly]

LGTM