Add Serialize & Deserialize to umbrella crate derive module (#7764)

When working with storage types that are to be set in the genesis block,
deriving serde::Serialize & serde::Deserialize is necessary (to my
knowledge). This PR introduces Serialize and Deserialize into the
umbrella crate derive (and indirectly prelude) module, allowing for
similar access as the other storage value derives.

---------

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Bastian Köcher <git@kchr.de>

Cargo.lock

@@ -16203,6 +16203,7 @@ dependencies = [
  "pallet-examples",
  "parity-scale-codec",
  "scale-info",
+ "serde",
  "sp-api 26.0.0",
  "sp-arithmetic 23.0.0",
  "sp-block-builder",

prdoc/pr_7764.prdoc

+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Add Serialize & Deserialize to umbrella crate derive module
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      This PR adds serde::Serialize and serde::Deserialize to the frame umbrella crate
+      `derive` and indirectly `prelude` modules. They can now be accessed through those.
+      Note: serde will still need to be added as a dependency in consuming crates. That or
+      you'll need to specify th `#[serde(crate = "PATH_TO_SERDE::serde")]` attribute at the
+      location where Serialize/Deserialize are used.
+
+crates:
+- name: polkadot-sdk-frame
+  bump: minor

substrate/frame/Cargo.toml

@@ -24,6 +24,7 @@ codec = { features = [
 scale-info = { features = [
 	"derive",
 ], workspace = true }
+serde = { workspace = true }
 
 # primitive deps, used for developing FRAME pallets.
 sp-arithmetic = { workspace = true }
@@ -95,6 +96,7 @@ std = [
 	"frame-try-runtime?/std",
 	"log/std",
 	"scale-info/std",
+	"serde/std",
 	"sp-api?/std",
 	"sp-arithmetic/std",
 	"sp-block-builder?/std",

substrate/frame/src/lib.rs

@@ -548,6 +548,13 @@ pub mod derive {
 		PartialOrdNoBound, RuntimeDebugNoBound,
 	};
 	pub use scale_info::TypeInfo;
+	pub use serde;
+	/// The `serde` `Serialize`/`Deserialize` derive macros and traits.
+	///
+	/// You will either need to add `serde` as a dependency in your crate's `Cargo.toml`
+	/// or specify the `#[serde(crate = "PATH_TO_THIS_CRATE::serde")]` attribute that points
+	/// to the path where serde can be found.
+	pub use serde::{Deserialize, Serialize};
 	pub use sp_runtime::RuntimeDebug;
 }