frame: support for serde added (#14261)

* frame: support for serde added

- enabled `serde` features in dependent crates, no gate feature introduced, linker should do the job and strip unused code.

- frame::staking: added impl of `serde::Serialize, serde::Deserialize` for `enum Forcing`

- primitives::runtime: impl_opaque_keys macro provides `Serialize/Deserialize` impl if `serde` is enabled

- primitives::staking: added impl of `serde::Serialize`, `serde::Deserialize` for `enum StakerStatus`

* frame::support: serde for pallets' GenesisConfig enabled in no-std

* Cargo.lock updated

* Update primitives/staking/Cargo.toml

Co-authored-by: Bastian Köcher <git@kchr.de>

* fix

* Cargo.lock update + missed serde/std in beefy

---------

Co-authored-by: Bastian Köcher <git@kchr.de>

substrate/frame/support/src/lib.rs

@@ -48,7 +48,6 @@ pub use once_cell;
 pub use paste;
 #[doc(hidden)]
 pub use scale_info;
-#[cfg(feature = "std")]
 pub use serde;
 pub use sp_api::metadata_ir;
 pub use sp_core::{OpaqueMetadata, Void};
@@ -821,7 +820,6 @@ macro_rules! assert_error_encoded_size {
 	} => {};
 }
 
-#[cfg(feature = "std")]
 #[doc(hidden)]
 pub use serde::{Deserialize, Serialize};