Move PalletVersion away from the crate version (#9165)

* Move `PalletVersion` away from the crate version

Before this pr, `PalletVersion` was referring to the crate version that
hosted the pallet. This pr introduces a custom `package.metadata.frame`
section in the `Cargo.toml` that can contain a `pallet-version` key
value pair. While the value is expected to be a valid u16. If this
key/value pair isn't given, the version is set to 1.

It also changes the `PalletVersion` declaration. We now only have one
`u16` that represents the version. Not a major/minor/patch version. As
the old `PalletVersion` was starting with the `u16` major, decoding the
old values will work.

* Overhaul the entire implementation

- Drop PalletVersion
- Introduce StorageVersion
- StorageVersion needs to be set in the crate and set for the macros
- Added migration

* Fix migrations

* Review feedback

* Remove unneeded dep

* remove pub consts

* Brings back logging and implements `GetStorageVersion`

* Return weight from migration

* Fmt and remove unused import

* Update frame/support/src/dispatch.rs

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* Update frame/support/src/traits/metadata.rs

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

substrate/frame/support/src/migrations.rs

@@ -0,0 +1,73 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2021 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use crate::{
+	traits::{GetStorageVersion, PalletInfoAccess},
+	weights::{RuntimeDbWeight, Weight},
+};
+
+/// Trait used by [`migrate_from_pallet_version_to_storage_version`] to do the actual migration.
+pub trait PalletVersionToStorageVersionHelper {
+	fn migrate(db_weight: &RuntimeDbWeight) -> Weight;
+}
+
+impl<T: GetStorageVersion + PalletInfoAccess> PalletVersionToStorageVersionHelper for T {
+	fn migrate(db_weight: &RuntimeDbWeight) -> Weight {
+		const PALLET_VERSION_STORAGE_KEY_POSTFIX: &[u8] = b":__PALLET_VERSION__:";
+
+		fn pallet_version_key(name: &str) -> [u8; 32] {
+			let pallet_name = sp_io::hashing::twox_128(name.as_bytes());
+			let postfix = sp_io::hashing::twox_128(PALLET_VERSION_STORAGE_KEY_POSTFIX);
+
+			let mut final_key = [0u8; 32];
+			final_key[..16].copy_from_slice(&pallet_name);
+			final_key[16..].copy_from_slice(&postfix);
+
+			final_key
+		}
+
+		sp_io::storage::clear(&pallet_version_key(<T as PalletInfoAccess>::name()));
+
+		let version = <T as GetStorageVersion>::current_storage_version();
+		version.put::<T>();
+
+		db_weight.writes(2)
+	}
+}
+
+#[impl_trait_for_tuples::impl_for_tuples(30)]
+impl PalletVersionToStorageVersionHelper for T {
+	fn migrate(db_weight: &RuntimeDbWeight) -> Weight {
+		let mut weight: Weight = 0;
+
+		for_tuples!( #( weight = weight.saturating_add(T::migrate(db_weight)); )* );
+
+		weight
+	}
+}
+
+/// Migrate from the `PalletVersion` struct to the new
+/// [`StorageVersion`](crate::traits::StorageVersion) struct.
+///
+/// This will remove all `PalletVersion's` from the state and insert the current storage version.
+pub fn migrate_from_pallet_version_to_storage_version<
+	AllPallets: PalletVersionToStorageVersionHelper,
+>(
+	db_weight: &RuntimeDbWeight,
+) -> Weight {
+	AllPallets::migrate(db_weight)
+}