Build script: replace string-based codegen with quote-based codegen

Cargo.toml

@@ -108,10 +108,14 @@ anyhow = "1.0.97"
 indexmap = { version = "2.8.0", features = ["serde"] }
 itertools = "0.14.0"
 once_cell = "1.20"
+prettyplease = "0.2.35"
+proc-macro2 = "1.0.95"
+quote = "1.0.40"
 regex = "1.10.6"
 serde = "1.0"
 serde_derive = "1.0"
 serde_with = { version = "3.12.0", default-features = false, features = ["macros"] }
+syn = { version = "2.0.104", features = ["full"] }
 toml = { version = "0.8.19", features = ["preserve_order"] }
 walkdir = "2.5"