contracts: Convert to framev2 macros (#8157)

* contracts: Convert to framev2

* Reduce the API surface of the crate

* Remove unused import

* Merge import block

* Use pallet::metadata to reduce metadata diff

* Remove the explicit "Null" from AccountCounter

substrate/bin/node/executor/tests/basic.rs

@@ -17,7 +17,6 @@
 
 use codec::{Encode, Decode, Joiner};
 use frame_support::{
-	StorageMap,
 	traits::Currency,
 	weights::{GetDispatchInfo, DispatchInfo, DispatchClass},
 };