Fix incorrect use of syn::exports (#7838)

* Fix incorrect use of syn::exports

Instead of using `syn::exports` we should import the trait from the
quote crate directly.

* Use own macro for test cases to fix compilation with latest syn

* Fix test

substrate/primitives/debug-derive/Cargo.toml

@@ -18,7 +18,7 @@ proc-macro = true
 
 [dependencies]
 quote = "1.0.3"
-syn = "1.0.7"
+syn = "1.0.58"
 proc-macro2 = "1.0"
 
 [features]