Update to syn 2 #871

Job	Run time
Doc tests	30s
Clippy	14s
rustfmt	13s
Minimal crates versions (stable, ubuntu)	29s
Minimal crates versions (stable, macOS)	30s
Test Rust stable on ubuntu	21s
Test features	39s
Minimal crates versions (stable, windows)	1m 12s
Test Rust stable on macOS	21s
Test Rust stable on windows	1m 2s
Test Rust nightly on ubuntu	17s
Test Rust nightly on macOS	21s
Test Rust nightly on windows	1m 0s
Test Rust 1.65.0 on ubuntu	1m 15s
Test Rust 1.65.0 on macOS	1m 14s
Test Rust 1.65.0 on windows	1m 17s
	10m 55s

Provide feedback