refactor: remove pytz and use standard library zoneinfo

[waketzheng]

Description

1. Latest version of Django does not depends on pytz
2. Python3.9 add a new module zoneinfo, which can be used to replace pytz

Motivation and Context

Reduce dependency suggested by #1956

How Has This Been Tested?

make ci

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added the changelog accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codspeed-hq]

Merging this PR will not alter performance

✅ 16 untouched benchmarks

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_{Comparing waketzheng:replace-pytz (47847f8) with develop (2aa8e0d)}

[coveralls]

Pull Request Test Coverage Report for Build 21782611814

Details

• 27 of 29 (93.1%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.05%) to 84.036%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
tortoise/backends/oracle/client.py	1	2	50.0%
tortoise/timezone.py	26	27	96.3%

Files with Coverage Reduction	New Missed Lines	%
tortoise/timezone.py	1	83.33%

Totals
Change from base Build 21736468513:	0.05%
Covered Lines:	9980
Relevant Lines:	11464

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💛 - Coveralls

[ockan]

0.25.3 nothing changed

[waketzheng]

0.25.3 nothing changed

@ockan This PR does not merge to develop branch yet. And it's a breaking change, will not release at 0.25.x, may be 0.26.0 or higher version (not promise)

[waketzheng]

Before these PRs merged, you can use the slim branch for clean deps:

uv pip install -U "tortoise-orm @git+ssh://git@github.com/tortoise/tortoise-orm@slim"

# Or by http:
#uv pip install -U "tortoise-orm @git+https://github.com/tortoise/tortoise-orm@slim"

This branch only depends on pypika-tortoise

[abondar]

Is there any reason to keep pytz as even optional dependency?

[waketzheng]

Is there any reason to keep pytz as even optional dependency?

Seem that is better to remove it. I updated code and add some tests.