Revert "FRAME: Create TransactionExtension as a replacement for SignedExtension (#2280)" (#3665)

This PR reverts #2280 which introduced `TransactionExtension` to replace
`SignedExtension`.

As a result of the discussion
[here](https://github.com/paritytech/polkadot-sdk/pull/3623#issuecomment-1986789700),
the changes will be reverted for now with plans to reintroduce the
concept in the future.

---------

Signed-off-by: georgepisaltu <george.pisaltu@parity.io>

substrate/client/api/src/notifications/tests.rs

@@ -18,10 +18,7 @@
 
 use super::*;
 
-use sp_runtime::{
-	generic::UncheckedExtrinsic,
-	testing::{Block as RawBlock, H256 as Hash},
-};
+use sp_runtime::testing::{Block as RawBlock, ExtrinsicWrapper, H256 as Hash};
 use std::iter::{empty, Empty};
 
 type TestChangeSet = (
@@ -53,7 +50,7 @@ impl PartialEq for StorageChangeSet {
 	}
 }
 
-type Block = RawBlock<UncheckedExtrinsic<u64, substrate_test_runtime::RuntimeCall, (), ()>>;
+type Block = RawBlock<ExtrinsicWrapper<Hash>>;
 
 #[test]
 fn triggering_change_should_notify_wildcard_listeners() {