Changed validity from &Option<Bitmap> to Option<&Bitmap>.

[jorgecarleitao]

Changed the signature of Array::validity() and MutableArray::validity(). IMO it makes the API a bit easier to use and aligned with other methods in std.

To migrate:

• Change validity().as_ref().unwrap() to validity().unwrap()
• Change validity().as_ref().map(...) to validity().map(...)
• Change validity().clone() to validity().cloned()
• Change &Option<Bitmap> to Option<&Bitmap>
• Change assert_eq!(validity, &None) to assert_eq!(validity, None)
• Change assert_eq!(validity, &Some(Bitmap(...)) to assert_eq!(validity, Some(&Bitmap(...)))

[codecov]

Codecov Report

Merging #431 (c45aa8c) into main (688e979) will increase coverage by 0.00%.
The diff coverage is 86.88%.

@@           Coverage Diff           @@
##             main     #431   +/-   ##
=======================================
  Coverage   80.77%   80.78%           
=======================================
  Files         372      372           
  Lines       22637    22637           
=======================================
+ Hits        18286    18288    +2     
+ Misses       4351     4349    -2     

Impacted Files	Coverage Δ
src/array/binary/mutable.rs	65.40% <0.00%> (ø)
src/array/dictionary/mutable.rs	82.14% <0.00%> (ø)
src/array/fixed_size_list/mutable.rs	40.38% <0.00%> (ø)
src/array/list/mutable.rs	75.86% <0.00%> (ø)
src/array/mod.rs	58.97% <ø> (ø)
src/array/utf8/mutable.rs	89.91% <0.00%> (ø)
src/compute/nullif.rs	0.00% <0.00%> (ø)
src/compute/sort/common.rs	92.85% <ø> (ø)
src/io/parquet/write/binary/basic.rs	85.13% <ø> (ø)
src/io/parquet/write/mod.rs	51.28% <0.00%> (ø)
... and 49 more

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[ritchie46]

IMO this makes sense. And is a patter you seem more often in std.

[jorgecarleitao]

cc @sundy-li @houqp since this affects your work on databend and datafusion, respectively.

[houqp]

LGTM, nice improvements.

[sundy-li]

LGTM