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/frame/system/src/lib.rs

@@ -166,7 +166,7 @@ pub use extensions::{
 	check_genesis::CheckGenesis, check_mortality::CheckMortality,
 	check_non_zero_sender::CheckNonZeroSender, check_nonce::CheckNonce,
 	check_spec_version::CheckSpecVersion, check_tx_version::CheckTxVersion,
-	check_weight::CheckWeight, WeightInfo as ExtensionsWeightInfo,
+	check_weight::CheckWeight,
 };
 // Backward compatible re-export.
 pub use extensions::check_mortality::CheckMortality as CheckEra;
@@ -284,7 +284,6 @@ pub mod pallet {
 			type OnNewAccount = ();
 			type OnKilledAccount = ();
 			type SystemWeightInfo = ();
-			type ExtensionsWeightInfo = ();
 			type SS58Prefix = ();
 			type Version = ();
 			type BlockWeights = ();
@@ -357,9 +356,6 @@ pub mod pallet {
 			/// Weight information for the extrinsics of this pallet.
 			type SystemWeightInfo = ();
 
-			/// Weight information for the extensions of this pallet.
-			type ExtensionsWeightInfo = ();
-
 			/// This is used as an identifier of the chain.
 			type SS58Prefix = ();
 
@@ -567,12 +563,8 @@ pub mod pallet {
 		/// All resources should be cleaned up associated with the given account.
 		type OnKilledAccount: OnKilledAccount<Self::AccountId>;
 
-		/// Weight information for the extrinsics of this pallet.
 		type SystemWeightInfo: WeightInfo;
 
-		/// Weight information for the transaction extensions of this pallet.
-		type ExtensionsWeightInfo: extensions::WeightInfo;
-
 		/// The designated SS58 prefix of this chain.
 		///
 		/// This replaces the "ss58Format" property declared in the chain spec. Reason is