Use zoneinfo for timezone handling instead of pytz

[saranti]

Pull Request Checklist

Thank you for taking the time to improve Arrow! Before submitting your pull request, please check all appropriate boxes:

• [ ] 🧪 Added tests for changed code.
• [x] 🛠️ All tests pass when run locally (run tox or make test to find out!).
• [x] 🧹 All linting checks pass when run locally (run tox -e lint or make lint to find out!).
• [ ] 📚 Updated documentation for changed code.
• [x] ⏩ Code is up-to-date with the master branch.

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Description of Changes

Closes #1175. Remove all pytz code and replace it with the equivalent from zoneinfo and use a backport for python versions <3.9.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (403c29f) to head (48eb157). Report is 13 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #1179   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           10        10           
  Lines         2324      2334   +10     
  Branches       357       357           
=========================================
+ Hits          2324      2334   +10     

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[jadchaar]

Hi @saranti mind getting this PR up to date? Then we can merge it in :)

[jadchaar]

Thanks @saranti , but it seems like the conflicts are still present and GH is not allowing us to re-run the actions to test

[saranti]

No worries. That looks better but it looks like there's a linting issue caused by https://github.com/arrow-py/arrow/commit/c2dfa12bde6bf8b097ad5bb369a0c71ae58a8386

[krisfremen]

No worries. That looks better but it looks like there's a linting issue caused by c2dfa12

Strange indeed, we might need to look at the linting actions and see why this got missed in the first place before merging.

https://github.com/arrow-py/arrow/pull/1202 Got a PR to revert that one @jadchaar

[jadchaar]

Odd indeed, this must have come as a result of the upgrades we made to the actions. I merged the revert, and updated branch @krisfremen. Would it be possible to reapply the PR you reverted once we merge?