feat: support primary_key/db_index and mark pk/index as deprecated

[waketzheng]

Description

Fixes TODOs in tortoise/fields/base.py

Motivation and Context

Rename Field argument pk/index to primary_key/db_index

How Has This Been Tested?

make ci && cd examples/fastapi && pytest _tests.py && cd ../blacksheep && pytest _tests.py

Checklist:

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

[coveralls]

Pull Request Test Coverage Report for Build 9189406969

Details

• 35 of 38 (92.11%) changed or added relevant lines in 4 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.002%) to 87.88%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
tortoise/contrib/mysql/fields.py	0	1	0.0%
tortoise/fields/base.py	21	23	91.3%
<!--	Total:	35	38	92.11%	-->

Files with Coverage Reduction	New Missed Lines	%
tortoise/fields/data.py	1	94.88%
<!--	Total:	1		-->

Totals
Change from base Build 9189055236:	-0.002%
Covered Lines:	5763
Relevant Lines:	6462

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💛 - Coveralls