Allow "anonymous" proxied accounts (#6236)

* Anonymous proxiers

* More testing

* More testing

* Build fix

* Build fix

* Benchmarks.

* fix benchmarking

* add weights

* fix line width

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

substrate/frame/support/src/traits.rs

@@ -47,10 +47,25 @@ impl<T> Filter<T> for () {
 pub trait InstanceFilter<T> {
 	/// Determine if a given value should be allowed through the filter (returns `true`) or not.
 	fn filter(&self, _: &T) -> bool;
+
+	/// Determines whether `self` matches at least all items that `o` does.
+	fn is_no_less_permissive(&self, o: &Self) -> bool { !self.is_less_permissive(o) }
+
+	/// Determines whether `self` matches at most only the items that `o` does.
+	fn is_no_more_permissive(&self, o: &Self) -> bool { !o.is_less_permissive(&self) }
+
+	/// Determines whether `self` matches all the items that `o` does and others.
+	fn is_more_permissive(&self, o: &Self) -> bool { o.is_less_permissive(self) }
+
+	/// Determines whether `self` does not match all the items that `_o` does, nor any others.
+	///
+	/// NOTE: This is the only `*permissive` function that needs to be reimplemented.
+	fn is_less_permissive(&self, _o: &Self) -> bool { true }
 }
 
 impl<T> InstanceFilter<T> for () {
 	fn filter(&self, _: &T) -> bool { true }
+	fn is_less_permissive(&self, _o: &Self) -> bool { false }
 }
 
 /// An abstraction of a value stored within storage, but possibly as part of a larger composite