perf: Several large parquet optimizations

[coastalwhite]

• Only verify UTF-8 on a dictionary page once (duh)
• Don't even worry about the page validity if it is never null
• Dispatch between pre-filter and post-filter for parallel=prefiltered.

[codecov]

Codecov Report

Attention: Patch coverage is 83.17073% with 69 lines in your changes missing coverage. Please review.

Project coverage is 79.87%. Comparing base (22a97bf) to head (7196ede).
Report is 52 commits behind head on main.

Files with missing lines	Patch %	Lines
...olars-parquet/src/arrow/read/deserialize/simple.rs	72.04%	26 Missing ⚠️
...et/src/arrow/read/deserialize/fixed_size_binary.rs	50.00%	7 Missing ⚠️
...arquet/src/arrow/read/deserialize/primitive/mod.rs	86.79%	7 Missing ⚠️
crates/polars-io/src/parquet/read/read_impl.rs	91.17%	6 Missing ⚠️
...et/src/arrow/read/deserialize/primitive/integer.rs	81.81%	6 Missing ⚠️
...lars-parquet/src/arrow/read/deserialize/binview.rs	86.84%	5 Missing ⚠️
...lars-parquet/src/arrow/read/deserialize/boolean.rs	75.00%	4 Missing ⚠️
.../polars-parquet/src/arrow/read/deserialize/null.rs	50.00%	3 Missing ⚠️
...s-parquet/src/arrow/read/deserialize/dictionary.rs	80.00%	2 Missing ⚠️
crates/polars-arrow/src/bitmap/bitmap_ops.rs	93.33%	1 Missing ⚠️
... and 2 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18437      +/-   ##
==========================================
- Coverage   79.91%   79.87%   -0.04%     
==========================================
  Files        1495     1496       +1     
  Lines      200261   200357      +96     
  Branches     2867     2867              
==========================================
+ Hits       160034   160042       +8     
- Misses      39681    39769      +88     
  Partials      546      546              

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[ritchie46]

Only verify UTF-8 on a dictionary page once (duh)

😄