fix: Deadlock due to bad logic in new-streaming join sampling

[orlp]

I introduced early stopping during the cached morsel flushing but this wasn't correct. I also didn't correctly re-label the sequence ids leading to potentially the same morsel id being sent into multiple pipelines.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 89 lines in your changes missing coverage. Please review.

Project coverage is 79.86%. Comparing base (9077aa4) to head (8503961).
Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-stream/src/nodes/joins/equi_join.rs	0.00%	89 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #21265      +/-   ##
==========================================
- Coverage   79.87%   79.86%   -0.01%     
==========================================
  Files        1596     1596              
  Lines      228469   228474       +5     
  Branches     2607     2607              
==========================================
- Hits       182487   182481       -6     
- Misses      45386    45397      +11     
  Partials      596      596              

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