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/bin/node/testing/src/bench.rs

@@ -51,7 +51,6 @@ use sp_core::{ed25519, sr25519, traits::SpawnNamed, Pair, Public};
 use sp_crypto_hashing::blake2_256;
 use sp_inherents::InherentData;
 use sp_runtime::{
-	generic::{ExtrinsicFormat, Preamble},
 	traits::{Block as BlockT, IdentifyAccount, Verify},
 	OpaqueExtrinsic,
 };
@@ -296,10 +295,10 @@ impl<'a> Iterator for BlockContentIterator<'a> {
 
 		let signed = self.keyring.sign(
 			CheckedExtrinsic {
-				format: ExtrinsicFormat::Signed(
+				signed: Some((
 					sender,
-					tx_ext(0, kitchensink_runtime::ExistentialDeposit::get() + 1),
-				),
+					signed_extra(0, kitchensink_runtime::ExistentialDeposit::get() + 1),
+				)),
 				function: match self.content.block_type {
 					BlockType::RandomTransfersKeepAlive =>
 						RuntimeCall::Balances(BalancesCall::transfer_keep_alive {
@@ -563,11 +562,11 @@ impl BenchKeyring {
 		tx_version: u32,
 		genesis_hash: [u8; 32],
 	) -> UncheckedExtrinsic {
-		match xt.format {
-			ExtrinsicFormat::Signed(signed, tx_ext) => {
+		match xt.signed {
+			Some((signed, extra)) => {
 				let payload = (
 					xt.function,
-					tx_ext.clone(),
+					extra.clone(),
 					spec_version,
 					tx_version,
 					genesis_hash,
@@ -582,20 +581,11 @@ impl BenchKeyring {
 					}
 				});
 				UncheckedExtrinsic {
-					preamble: Preamble::Signed(
-						sp_runtime::MultiAddress::Id(signed),
-						signature,
-						tx_ext,
-					),
+					signature: Some((sp_runtime::MultiAddress::Id(signed), signature, extra)),
 					function: payload.0,
 				}
 			},
-			ExtrinsicFormat::Bare =>
-				UncheckedExtrinsic { preamble: Preamble::Bare, function: xt.function },
-			ExtrinsicFormat::General(tx_ext) => UncheckedExtrinsic {
-				preamble: sp_runtime::generic::Preamble::General(tx_ext),
-				function: xt.function,
-			},
+			None => UncheckedExtrinsic { signature: None, function: xt.function },
 		}
 	}