chore: add __repr__ to Index class

[waketzheng]

Description

1. Add __repr__ to the Index class
2. Update type hint for the fields argument in Index __init__ to support both tuple[str, ...] and list[str] instead of only tuple[str, ...]
3. tests/contrib/test_pydantic.py and tests/testmodels.py was auto changed by make style

Motivation and Context

Without the custom __repr__, Index class display like this:

--> python -m IPython
Python 3.10.12 (main, Nov  6 2024, 20:22:13) [GCC 11.4.0]
Type 'copyright', 'credits' or 'license' for more information
IPython 8.30.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: from tortoise.indexes import Index

In [2]: Index(fields=('id',))
Out[2]: <tortoise.indexes.Index at 0x7ff40999ed40>

After it added:

In [1]: from tortoise.indexes import Index

In [2]: Index(fields=('id',))
Out[2]: Index(fields=['id'])

In [3]: idx = Index(fields=('id', 'name'))

In [4]: f'{idx = }'
Out[4]: "idx = Index(fields=['id', 'name'])"

How Has This Been Tested?

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.

[coveralls]

Pull Request Test Coverage Report for Build 12454956827

Details

• 11 of 11 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.04%) to 90.181%

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Totals
Change from base Build 12437576482:	0.04%
Covered Lines:	6392
Relevant Lines:	6973

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💛 - Coveralls