Generate storage info for pallet babe (#9760)

* Adding MaxEncodedLen for:
* NextConfigDescriptor
* AllowedSlots
* BabeEpochConfiguration

In prepation for adding storage information on pallet babe

* Adding stotage_info to pallet babe

Refactored UNDER_CONSTRUCTION_SEGMENT_LENGTH to become a runtime
parameter MaxSegmentLength

* Reinstate Slice as opposed to Vec

* Refactoring code to make it neater

* Replace `MaxSegmentLength` by
`UNDER_CONSTRUCTION_SEGMENT_LENGTH`
Stop exposing the bounds to the runtime

* Removing extra line

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

substrate/primitives/consensus/babe/src/digests.rs

@@ -21,7 +21,7 @@ use super::{
 	AllowedSlots, AuthorityId, AuthorityIndex, AuthoritySignature, BabeAuthorityWeight,
 	BabeEpochConfiguration, Slot, BABE_ENGINE_ID,
 };
-use codec::{Codec, Decode, Encode};
+use codec::{Codec, Decode, Encode, MaxEncodedLen};
 use sp_runtime::{DigestItem, RuntimeDebug};
 use sp_std::vec::Vec;
 
@@ -134,7 +134,9 @@ pub struct NextEpochDescriptor {
 
 /// Information about the next epoch config, if changed. This is broadcast in the first
 /// block of the epoch, and applies using the same rules as `NextEpochDescriptor`.
-#[derive(Decode, Encode, PartialEq, Eq, Clone, RuntimeDebug, scale_info::TypeInfo)]
+#[derive(
+	Decode, Encode, PartialEq, Eq, Clone, RuntimeDebug, MaxEncodedLen, scale_info::TypeInfo,
+)]
 pub enum NextConfigDescriptor {
 	/// Version 1.
 	#[codec(index = 1)]