refactor: Add sinked paths callback

[nameexhaustion]

For sink_iceberg / polars cloud.

pl.LazyFrame({"a": [0, 1, 2, 3, 4]}).sink_parquet(
    pl.PartitionBy(
        ".env/_data_out/partitioned",
        key="a",
    ),
    _sinked_paths_callback=pprint,
)

# SinkedPathsCallbackArgs(paths=['.env/_data_out/partitioned/a=2/00000000.parquet',
#                                '.env/_data_out/partitioned/a=3/00000000.parquet',
#                                '.env/_data_out/partitioned/a=0/00000000.parquet',
#                                '.env/_data_out/partitioned/a=4/00000000.parquet',
#                                '.env/_data_out/partitioned/a=1/00000000.parquet'])

[codecov]

Codecov Report

❌ Patch coverage is 95.76271% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.78%. Comparing base (cd9de5d) to head (22009cd).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-plan/src/dsl/options/sink.rs	90.47%	2 Missing ⚠️
...es/io_sinks/pipeline_initialization/single_file.rs	89.47%	2 Missing ⚠️
...s/io_sinks/pipeline_initialization/partition_by.rs	93.75%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #26995      +/-   ##
==========================================
- Coverage   81.78%   81.78%   -0.01%     
==========================================
  Files        1809     1810       +1     
  Lines      249417   249518     +101     
  Branches     3141     3141              
==========================================
+ Hits       203980   204057      +77     
- Misses      44632    44656      +24     
  Partials      805      805              

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[ritchie46]

Thinking aloud here, but can we make this callback only exists in IR? I don't think it should live in DSL.