* Introduce stacked filtering.

* Benchmarks

* Remove unneeded crates

* Fix proxy type's permissiveness checks.

* Repot multisig to make utility stateless.

* Repot filter stack impl into macro

* Fix wasm build

* Tests

* Final test.

* Tests for the macro

* Fix test

* Line width

* Fix

* Update frame/multisig/src/benchmarking.rs

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

* Update primitives/std/with_std.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Grumble

* Update frame/support/src/traits.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Update frame/support/src/traits.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Update frame/support/src/traits.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Update frame/support/src/traits.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Update frame/support/src/traits.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Update frame/multisig/src/tests.rs

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

* Update frame/multisig/src/tests.rs

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

* Grumble

* Migration

* Grumble

* Comments

* Migration

* Fix

* Fix

* Line width

* Allow unused

* Update frame/multisig/src/lib.rs

Co-authored-by: Alexander Popiak <alexander.popiak@parity.io>

* Fix up grumble.

* Remove Utility constraint in NonTransfer

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Alexander Popiak <alexander.popiak@parity.io>