[#2724] refactor(spark): Introduce ReassignExecutor to simplify shuffle writer logic

[zuston]

What changes were proposed in this pull request?

Introduce ReassignExecutor to clarify shuffle writer logic

Why are the changes needed?

for #2724

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Existing tests

[github-actions]

Test Results

 3 185 files  +10   3 185 suites  +10   6h 51m 49s ⏱️ +42s
 1 243 tests + 2   1 242 ✅ + 2   1 💤 ±0  0 ❌ ±0 
15 754 runs  +20  15 739 ✅ +20  15 💤 ±0  0 ❌ ±0 

Results for commit af0f40e. ± Comparison against base commit eb53a1a.

♻️ This comment has been updated with latest results.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 23.38308% with 154 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.57%. Comparing base (69b1b45) to head (a46d5cf).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...a/org/apache/uniffle/shuffle/ReassignExecutor.java	23.61%	145 Missing and 7 partials ⚠️
...pache/spark/shuffle/writer/WriteBufferManager.java	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2727      +/-   ##
============================================
- Coverage     52.00%   50.57%   -1.43%     
+ Complexity     3566     3276     -290     
============================================
  Files           554      533      -21     
  Lines         29448    25740    -3708     
  Branches       2739     2344     -395     
============================================
- Hits          15315    13019    -2296     
+ Misses        13133    11878    -1255     
+ Partials       1000      843     -157     

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