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/frame/support/procedural/tools/Cargo.toml

@@ -15,5 +15,5 @@ targets = ["x86_64-unknown-linux-gnu"]
 frame-support-procedural-tools-derive = { version = "2.0.0", path = "./derive" }
 proc-macro2 = "1.0.6"
 quote = "1.0.3"
-syn = { version = "1.0.7", features = ["full", "visit"] }
+syn = { version = "1.0.58", features = ["full", "visit"] }
 proc-macro-crate = "0.1.5"

substrate/frame/support/procedural/tools/derive/Cargo.toml

@@ -17,4 +17,4 @@ proc-macro = true
 [dependencies]
 proc-macro2 = "1.0.6"
 quote = { version = "1.0.3", features = ["proc-macro"] }
-syn = { version = "1.0.7", features = ["proc-macro" ,"full", "extra-traits", "parsing"] }
+syn = { version = "1.0.58", features = ["proc-macro" ,"full", "extra-traits", "parsing"] }