refactor(rust): Remove short-lived / non-CPU bound task spawns on async executor in new-streaming

[nameexhaustion]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 23 lines in your changes missing coverage. Please review.

Project coverage is 79.86%. Comparing base (4894e24) to head (88ecaf4).
Report is 39 commits behind head on main.

Files with missing lines	Patch %	Lines
...tes/polars-stream/src/nodes/parquet_source/init.rs	0.00%	12 Missing ⚠️
...m/src/nodes/parquet_source/row_group_data_fetch.rs	0.00%	5 Missing ⚠️
...ates/polars-stream/src/nodes/parquet_source/mod.rs	0.00%	3 Missing ⚠️
...tream/src/nodes/parquet_source/row_group_decode.rs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18764      +/-   ##
==========================================
+ Coverage   79.85%   79.86%   +0.01%     
==========================================
  Files        1517     1517              
  Lines      205530   205516      -14     
  Branches     2892     2892              
==========================================
+ Hits       164119   164132      +13     
+ Misses      40863    40836      -27     
  Partials      548      548              

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