Update treasury weights. (#5723)

* treasury weight formula

* use max tippers count

* doc

* Fix upper bound

* rounding a bit

* remove unused + doc

* as u64 -> as Weight

* 2 significative digits rounded up

* rename ContainsCountUpperBound -> ContainsLengthBound

* add doc

* sender account -> origin account

* fix

substrate/frame/elections-phragmen/src/lib.rs

@@ -93,6 +93,7 @@ use frame_support::{
 	traits::{
 		Currency, Get, LockableCurrency, LockIdentifier, ReservableCurrency, WithdrawReasons,
 		ChangeMembers, OnUnbalanced, WithdrawReason, Contains, BalanceStatus, InitializeMembers,
+		ContainsLengthBound,
 	}
 };
 use sp_phragmen::{build_support_map, ExtendedBalance, VoteWeight, PhragmenResult};
@@ -880,6 +881,15 @@ impl<T: Trait> Contains<T::AccountId> for Module<T> {
 	}
 }
 
+impl<T: Trait> ContainsLengthBound for Module<T> {
+	fn min_len() -> usize { 0 }
+
+	/// Implementation uses a parameter type so calling is cost-free.
+	fn max_len() -> usize {
+		Self::desired_members() as usize
+	}
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;