refactor(css_parser): Renamed 'CssSimpleFunction' to 'CssFunction'

[denbezrukov]

Summary

Renamed 'CssSimpleFunction' to 'CssFunction'.
All instances of 'CssSimpleFunction' have been replaced with 'CssFunction' across multiple files. This includes updates to function names, variable names, and type annotations.

Test Plan

cargo test

[netlify]

✅ Deploy Preview for biomejs canceled.

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🔨 Latest commit	260e74c
🔍 Latest deploy log	https://app.netlify.com/sites/biomejs/deploys/65a91bd957450100086de4e5

[github-actions]

Parser conformance results on

js/262

Test result	main count	This PR count	Difference
Total	49701	49701	0
Passed	48721	48721	0
Failed	980	980	0
Panics	0	0	0
Coverage	98.03%	98.03%	0.00%

jsx/babel

Test result	main count	This PR count	Difference
Total	40	40	0
Passed	37	37	0
Failed	3	3	0
Panics	0	0	0
Coverage	92.50%	92.50%	0.00%

symbols/microsoft

Test result	main count	This PR count	Difference
Total	6322	6322	0
Passed	2036	2036	0
Failed	4286	4286	0
Panics	0	0	0
Coverage	32.20%	32.20%	0.00%

ts/babel

Test result	main count	This PR count	Difference
Total	662	662	0
Passed	592	592	0
Failed	70	70	0
Panics	0	0	0
Coverage	89.43%	89.43%	0.00%

ts/microsoft

Test result	main count	This PR count	Difference
Total	17646	17646	0
Passed	13452	13452	0
Failed	4192	4192	0
Panics	2	2	0
Coverage	76.23%	76.23%	0.00%

[codspeed-hq]

CodSpeed Performance Report

Merging #1588 will not alter performance

_{Comparing refactor/css-function (260e74c) with main (09db855)}

Summary

✅ 93 untouched benchmarks