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>

cumulus/test/service/src/bench_utils.rs

@@ -69,7 +69,7 @@ pub fn extrinsic_set_time(client: &TestClient) -> OpaqueExtrinsic {
 
 	let timestamp = best_number as u64 * cumulus_test_runtime::MinimumPeriod::get();
 	cumulus_test_runtime::UncheckedExtrinsic {
-		preamble: sp_runtime::generic::Preamble::Bare,
+		signature: None,
 		function: cumulus_test_runtime::RuntimeCall::Timestamp(pallet_timestamp::Call::set {
 			now: timestamp,
 		}),
@@ -102,7 +102,7 @@ pub fn extrinsic_set_validation_data(
 	};
 
 	cumulus_test_runtime::UncheckedExtrinsic {
-		preamble: sp_runtime::generic::Preamble::Bare,
+		signature: None,
 		function: cumulus_test_runtime::RuntimeCall::ParachainSystem(
 			cumulus_pallet_parachain_system::Call::set_validation_data { data },
 		),