[FEAT] Enable concat for swordfish

[colin-ho]

Implement concat as a streaming sink in swordfish.

Concatenating two dataframes in a streaming executor is pretty simple. You just stream the left side, then stream the right side. This PR implements just that.

[codspeed-hq]

CodSpeed Performance Report

Merging #2976 will not alter performance

_{Comparing colin/swordfish-concat (102970e) with main (31d5412)}

Summary

✅ 17 untouched benchmarks

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.63%. Comparing base (31d5412) to head (102970e).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2976      +/-   ##
==========================================
+ Coverage   77.35%   78.63%   +1.28%     
==========================================
  Files         615      616       +1     
  Lines       74412    73147    -1265     
==========================================
- Hits        57561    57520      -41     
+ Misses      16851    15627    -1224     

Files with missing lines	Coverage Δ
src/daft-local-execution/src/pipeline.rs	94.30% <100.00%> (+0.44%)	⬆️
src/daft-local-execution/src/sinks/concat.rs	100.00% <100.00%> (ø)
...c/daft-local-execution/src/sinks/streaming_sink.rs	80.15% <ø> (ø)

... and 17 files with indirect coverage changes

[kevinzwang]

LGTM. One todo for the future: loosen index ordering requirement when downstream ops do not need data to be ordered. That way the right side can start computation before the left side is done.