Update versions and CHANGELOG for 16.0.0

[alamb]

Re #1809

See rendered changelog here: https://github.com/alamb/arrow-rs/blob/alamb/prepare_for_16.0.0/CHANGELOG.md

[codecov-commenter]

Codecov Report

Merging #1826 (90866fe) into master (8f1fd12) will not change coverage.
The diff coverage is n/a.

❗ Current head 90866fe differs from pull request most recent head 81c009a. Consider uploading reports for the commit 81c009a to get more accurate results

@@           Coverage Diff           @@
##           master    #1826   +/-   ##
=======================================
  Coverage   83.45%   83.45%           
=======================================
  Files         200      200           
  Lines       56697    56697           
=======================================
  Hits        47315    47315           
  Misses       9382     9382           

Impacted Files	Coverage Δ
arrow/src/datatypes/datatype.rs	65.42% <0.00%> (-0.38%)	⬇️
parquet_derive/src/parquet_field.rs	66.21% <0.00%> (+0.22%)	⬆️

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