refactor: use zoneinfo instead of pytz

[waketzheng]

Description

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]

CodSpeed Performance Report

Merging #2023 will not alter performance

_{Comparing waketzheng:replace-pytz (cc77a36) with develop (1d2400b)}

Summary

✅ 16 untouched

[coveralls]

Pull Request Test Coverage Report for Build 20632763389

Details

• 21 of 29 (72.41%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.03%) to 90.717%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
tortoise/backends/oracle/client.py	1	2	50.0%
tortoise/timezone.py	20	27	74.07%

Files with Coverage Reduction	New Missed Lines	%
tortoise/timezone.py	1	73.81%

Totals
Change from base Build 20588671038:	-0.03%
Covered Lines:	6652
Relevant Lines:	7218

---

💛 - 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://[email protected]/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