Improve truncate_models for cascade delete

[abondar]

Truncate with cascade, so function is more useful in tests

[codspeed-hq]

Merging this PR will not alter performance

✅ 24 untouched benchmarks

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_{Comparing tech/improve-truncate (2e8836c) with develop (0b516dd)}

[coveralls]

Pull Request Test Coverage Report for Build 21918966412

Details

• 43 of 45 (95.56%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 82.669%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
tortoise/contrib/test/init.py	43	45	95.56%

Totals
Change from base Build 21916500717:	0.1%
Covered Lines:	10541
Relevant Lines:	12287

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💛 - Coveralls