refactor(rust): Add new streaming CSV source

[nameexhaustion]

Adds a simple CSV source - we have one thread scanning for line batches which get sent to other threads for parsing

The performance is mostly equivalent with the in-memory-engine, except for one very specific type of query -

q = pl.scan_csv(path_base + "yellow_tripdata_2015-01.csv").slice(10_000_000)
print(q.collect())
# shape: (2_748_986, 19)

# 9.60s user 1.47s system 1093% cpu 1.012 total # in-memory engine
# 2.23s user 0.41s system  414% cpu 0.638 total # new-streaming engine

[nameexhaustion]

some minor drive-by refactors of parquet source

[nameexhaustion]

This unwrap() is not ideal, but I don't currently have any good ideas on how to avoid this

[codecov]

Codecov Report

Attention: Patch coverage is 1.52381% with 517 lines in your changes missing coverage. Please review.

Project coverage is 79.37%. Comparing base (8cb7839) to head (644dbd9).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-stream/src/nodes/csv_source.rs	0.00%	486 Missing ⚠️
...s/polars-stream/src/async_primitives/wait_group.rs	0.00%	16 Missing ⚠️
py-polars/polars/io/csv/functions.py	37.50%	6 Missing and 4 partials ⚠️
...tes/polars-stream/src/nodes/parquet_source/init.rs	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19694      +/-   ##
==========================================
- Coverage   79.55%   79.37%   -0.19%     
==========================================
  Files        1544     1545       +1     
  Lines      213240   213735     +495     
  Branches     2441     2445       +4     
==========================================
+ Hits       169643   169647       +4     
- Misses      43048    43536     +488     
- Partials      549      552       +3     

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