[cumulus] parachains-common testnet constants cleaning (#3134)

The `parachains-common` contains a lots of constants and type
definitions which are used for `polkadot-sdk`'s testnet runtimes and
also for `polkadot-fellows`'s production [SP
runtimes](https://github.com/polkadot-fellows/runtimes/tree/main/system-parachains/constants).
This PR cleans `parachains-common` module to contain only common and
generic functionality.

Testnet-specific constants have been moved to the separate module
dedicated just for testnets:
`polkadot-sdk/cumulus/parachains/runtimes/constants/`


Part of: https://github.com/paritytech/polkadot-sdk/issues/3054

---------

Co-authored-by: georgepisaltu <george.pisaltu@parity.io>

cumulus/parachains/runtimes/people/people-rococo/src/lib.rs

@@ -43,7 +43,6 @@ use pallet_xcm::{EnsureXcm, IsVoiceOfBody};
 use parachains_common::{
 	impls::DealWithFees,
 	message_queue::{NarrowOriginToSibling, ParaIdToSibling},
-	rococo::{consensus::*, currency::*, fee::WeightToFee},
 	AccountId, Balance, BlockNumber, Hash, Header, Nonce, Signature, AVERAGE_ON_INITIALIZE_RATIO,
 	HOURS, MAXIMUM_BLOCK_WEIGHT, NORMAL_DISPATCH_RATIO, SLOT_DURATION,
 };
@@ -64,6 +63,7 @@ use sp_std::prelude::*;
 #[cfg(feature = "std")]
 use sp_version::NativeVersion;
 use sp_version::RuntimeVersion;
+use testnet_parachains_constants::rococo::{consensus::*, currency::*, fee::WeightToFee};
 use weights::{BlockExecutionWeight, ExtrinsicBaseWeight, RocksDbWeight};
 use xcm::latest::prelude::BodyId;
 use xcm_config::{