frame: GenesisBuild::build allowed in no_std (#14107)

* frame: GenesisBuild::build allowed in no_std

i`GenesisBuild::build` function will be required for no_std in no native
runtime world.

`GenesisBuild::build` macro generated function allows to build the runtime
GenesisConfig assembled from all pallets' GenesisConfigs.

* fixes

* GenesisBuild::build avaiable in no-std

- #[cfg(feature = "std")] is not longer added to GenesisBuild implementation.

* system: hash69 available for no-std

* elections-phragmen: panic message fixed for no_std

* frame::suport: doc updated

* test-runtime: default for GenesisConfig

* frame::test-pallet: serde/std added to std feature deps

* Cargo.toml: deps sorted

* Cargo.lock update

cargo update -p frame-support-test-pallet -p frame-support-test

* frame ui tests: cleanup

---------

Co-authored-by: parity-processbot <>

substrate/frame/system/src/lib.rs

@@ -707,7 +707,6 @@ pub struct EventRecord<E: Parameter + Member, T> {
 
 // Create a Hash with 69 for each byte,
 // only used to build genesis config.
-#[cfg(feature = "std")]
 fn hash69<T: AsMut<[u8]> + Default>() -> T {
 	let mut h = T::default();
 	h.as_mut().iter_mut().for_each(|byte| *byte = 69);