Rewrite `style.rs` using `syn` #592

Job	Run time
Style check	1m 13s
Check #[cfg]s	13s
Test tier1 (i686-unknown-linux-gnu, true, ubuntu-24.04)	4m 1s
Verify build (stable, ubuntu-24.04)	2m 54s
Test tier1 (x86_64-unknown-linux-gnu, true, ubuntu-24.04)	3m 27s
Verify build (stable, macos-14)	28s
Test tier1 (aarch64-apple-darwin, macos-14)	1m 43s
Verify build (stable, windows-2022)	3m 36s
Test tier1 (x86_64-pc-windows-gnu, windows-2022, 64, x86_64)	3m 54s
Test tier1 (x86_64-pc-windows-msvc, windows-2022)	3m 52s
Verify build (nightly, ubuntu-24.04)	17m 55s
Test tier1 (i686-pc-windows-msvc, windows-2022)	3m 57s
Verify build (nightly, macos-14)	56s
Verify build (nightly, windows-2022)	3m 47s
Verify build (1.63.0, ubuntu-24.04)	4m 56s
Verify build (1.63.0, macos-14)	1m 32s
Verify build (1.63.0, windows-2022)	6m 50s
Verify build (beta, ubuntu-24.04)	2m 42s
Test tier2	0s
Test tier2 VM	0s
success	1s
	1h 7m 57s

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