refactor(rust): Rename data_type -> dtype

[nameexhaustion]

Consistently use dtype internally

[codecov]

Codecov Report

Attention: Patch coverage is 75.95721% with 427 lines in your changes missing coverage. Please review.

Project coverage is 79.84%. Comparing base (242d30a) to head (a04fa51).
Report is 30 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-arrow/src/compute/temporal.rs	35.29%	22 Missing ⚠️
...olars-parquet/src/arrow/read/deserialize/simple.rs	65.57%	21 Missing ⚠️
...olars-parquet/src/arrow/read/deserialize/nested.rs	59.52%	17 Missing ⚠️
crates/polars-arrow/src/ffi/schema.rs	60.97%	16 Missing ⚠️
crates/polars-core/src/chunked_array/cast.rs	79.41%	14 Missing ⚠️
crates/polars-arrow/src/compute/arity.rs	25.00%	12 Missing ⚠️
crates/polars-arrow/src/array/mod.rs	75.55%	11 Missing ⚠️
crates/polars-arrow/src/io/ipc/read/deserialize.rs	56.00%	11 Missing ⚠️
crates/polars-arrow/src/mmap/array.rs	42.10%	11 Missing ⚠️
crates/polars-arrow/src/compute/cast/binary_to.rs	16.66%	10 Missing ⚠️
... and 102 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18566      +/-   ##
==========================================
- Coverage   79.86%   79.84%   -0.02%     
==========================================
  Files        1501     1501              
  Lines      201958   201707     -251     
  Branches     2869     2869              
==========================================
- Hits       161290   161056     -234     
+ Misses      40122    40105      -17     
  Partials      546      546              

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