Make offchain indexing work (#7940)

* Make offchain indexing work

This fixes some bugs with offchain indexing to make it actually working ;)

* Fix tests

* Fix browser build

* Update client/db/src/offchain.rs

Co-authored-by: cheme <emericchevalier.pro@gmail.com>

* Remove seperation between prefix and key

Co-authored-by: cheme <emericchevalier.pro@gmail.com>

substrate/primitives/api/src/lib.rs

@@ -47,8 +47,6 @@ pub use sp_core::NativeOrEncoded;
 #[doc(hidden)]
 #[cfg(feature = "std")]
 pub use hash_db::Hasher;
-#[cfg(feature = "std")]
-pub use sp_core::offchain::storage::OffchainOverlayedChanges;
 #[doc(hidden)]
 #[cfg(not(feature = "std"))]
 pub use sp_core::to_substrate_wasm_fn_return_value;
@@ -521,8 +519,6 @@ pub struct CallApiAtParams<'a, Block: BlockT, C, NC, Backend: StateBackend<HashF
 	pub arguments: Vec<u8>,
 	/// The overlayed changes that are on top of the state.
 	pub overlayed_changes: &'a RefCell<OverlayedChanges>,
-	/// The overlayed changes to be applied to the offchain worker database.
-	pub offchain_changes: &'a RefCell<OffchainOverlayedChanges>,
 	/// The cache for storage transactions.
 	pub storage_transaction_cache: &'a RefCell<StorageTransactionCache<Block, Backend>>,
 	/// Determines if the function requires that `initialize_block` should be called before calling