refactor(stream): implement LocalSimpleAgg without AggExecutor

[TennyZhuang]

Signed-off-by: TennyZhuang zty0826@gmail.com

What's changed and what's your intention?

PLEASE DO NOT LEAVE THIS EMPTY !!!

We can try to remove AggExecutorWrapper in executor_v2, due to the following reasons:

1. The AggExecutorWrapper almost do nothing in executor_v2.
2. We need to split chunks in HashAgg, the original AggExecutor will not work.
3. The implementation based on the original AggExecutorWrapper still looks like a state machine.

We may investigate how to reduce the common codes in executor_v2 later.

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)

[pleiadesian]

LGTM

[BugenZhao]

3. The implementation based on the original AggExecutorWrapper still looks like a state machine.

Most migrated executors are simply moved to the new directory and the only changes might be the input type currently. I believe a deep review or rewrite might be required.

[codecov]

Codecov Report

Merging #1823 (585e093) into main (2458c0e) will decrease coverage by 0.01%.
The diff coverage is 98.14%.

@@            Coverage Diff             @@
##             main    #1823      +/-   ##
==========================================
- Coverage   70.72%   70.70%   -0.02%     
==========================================
  Files         611      611              
  Lines       79896    79861      -35     
==========================================
- Hits        56503    56469      -34     
+ Misses      23393    23392       -1     

Flag	Coverage Δ
rust	70.70% <98.14%> (-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/local_simple_agg.rs	96.66% <98.14%> (-1.01%)	⬇️
src/connector/src/filesystem/file_common.rs	80.88% <0.00%> (+0.88%)	⬆️

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