Use pypika's SqlContext to improve performance

[henadzit]

Description

• Update the code to use pypika's SqlContext

⚠️ This PR depends on the pypika PR, and should not be merged until it is merged.

Motivation and Context

This PR improves the performance of SQL generation by pypika (see the Codspeed comment for more details), hence improving over query performance:

• 23% improvement in the test_get_many_fields benchmark
• 9% improvement in the test_filter_many_filters benchmark
• 4% improvement in test_filter_few_fields

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 #1837 will improve performances by 23.45%

_{Comparing henadzit:feat/pypika-sql-context (f81336d) with develop (7afc90e)}

Summary

⚡ 1 improvements
✅ 7 untouched benchmarks

Benchmarks breakdown

	Benchmark	develop	henadzit:feat/pypika-sql-context	Change
⚡	test_get_many_fields	1.5 ms	1.2 ms	+23.45%

[coveralls]

Pull Request Test Coverage Report for Build 12597288641

Details

• 26 of 29 (89.66%) changed or added relevant lines in 8 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage remained the same at 90.145%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
tortoise/backends/mysql/executor.py	2	3	66.67%
tortoise/indexes.py	0	2	0.0%

Files with Coverage Reduction	New Missed Lines	%
tortoise/indexes.py	1	84.29%

Totals
Change from base Build 12596506172:	0.0%
Covered Lines:	6465
Relevant Lines:	7054

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💛 - Coveralls