refactor(streaming): implement GlobalSimpleAgg without AggExecutor

[pleiadesian]

Signed-off-by: Zulai Wang zl31wang@gmail.com

What's changed and what's your intention?

As title.

Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests

Refer to a related PR or issue link (optional)

#1886

[codecov]

Codecov Report

Merging #1887 (f023542) into main (ecbd5a5) will decrease coverage by 0.01%.
The diff coverage is 98.03%.

@@            Coverage Diff             @@
##             main    #1887      +/-   ##
==========================================
- Coverage   70.71%   70.70%   -0.02%     
==========================================
  Files         610      610              
  Lines       79844    79832      -12     
==========================================
- Hits        56465    56446      -19     
- Misses      23379    23386       +7     

Flag	Coverage Δ
rust	70.70% <98.03%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/stream/src/executor_v2/global_simple_agg.rs	96.91% <98.03%> (-0.16%)	⬇️
...stream/src/executor_v2/aggregation/agg_executor.rs	85.39% <0.00%> (-5.06%)	⬇️
src/meta/src/manager/epoch.rs	83.01% <0.00%> (+3.77%)	⬆️

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[TennyZhuang]

LGTM, but CI failed