Prepare for 18.0.0 release: Update CHANGELOG and versions

[alamb]

Which issue does this PR close?

RE #1952

Rationale for this change

Prepares for release of version 18.0.0

What changes are included in this PR?

1. Update CHANGELOG (see rendered version here: https://github.com/alamb/arrow-rs/blob/alamb/prepare_for_18.0.0/CHANGELOG.md)
2. Update version to 18.0.0

Are there any user-facing changes?

Yes

[alamb]

I plan to update the CHANGELOG (based on titles of tickets) one last time tomorrow (Friday July 8, 2022) prior to merging this PR and cutting a release

FWIW here is the command I will run

CHANGELOG_GITHUB_TOKEN=$ARROW_GITHUB_API_TOKEN ./dev/release/update_change_log.sh

[codecov-commenter]

Codecov Report

Merging #2023 (03c5aa6) into master (d70c2ea) will decrease coverage by 0.00%.
The diff coverage is 84.68%.

❗ Current head 03c5aa6 differs from pull request most recent head 45e4927. Consider uploading reports for the commit 45e4927 to get more accurate results

@@            Coverage Diff             @@
##           master    #2023      +/-   ##
==========================================
- Coverage   83.54%   83.54%   -0.01%     
==========================================
  Files         222      222              
  Lines       58095    58178      +83     
==========================================
+ Hits        48537    48604      +67     
- Misses       9558     9574      +16     

Impacted Files	Coverage Δ
arrow/src/array/equal_json.rs	87.89% <0.00%> (-1.81%)	⬇️
arrow/src/array/iterator.rs	96.11% <ø> (ø)
arrow/src/array/mod.rs	100.00% <ø> (ø)
arrow/src/array/ord.rs	69.17% <ø> (ø)
arrow/src/compute/kernels/cast.rs	95.79% <ø> (ø)
arrow/src/compute/kernels/sort.rs	95.67% <ø> (ø)
arrow/src/compute/kernels/take.rs	95.27% <ø> (ø)
arrow/src/csv/reader.rs	89.89% <ø> (ø)
arrow/src/util/decimal.rs	91.50% <ø> (ø)
arrow/src/util/display.rs	73.17% <ø> (ø)
... and 6 more

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[viirya]

@alamb Can we also put #1982 into 18.0.0 release? So add, subtract, multiply and divide can be supported together in this new release. Thanks.

[alamb]

@alamb Can we also put #1982 into 18.0.0 release? So add, subtract, multiply and divide can be supported together in this new release. Thanks.

Sure thing @viirya -- thanks. I'll rerun the release notes script later today as well