Several tweaks needed for Governance 2.0 (#11124)

* Add stepped curve for referenda

* Treasury SpendOrigin

* Add tests

* Better Origin Or-gating

* Reciprocal curve

* Tests for reciprical and rounding in PerThings

* Tweaks and new quad curve

* Const derivation of reciprocal curve parameters

* Remove some unneeded code

* Actually useful linear curve

* Fixes

* Provisional curves

* Rejig 'turnout' as 'support'

* Use TypedGet

* Fixes

* Enable curve's ceil to be configured

* Formatting

* Fixes

* Fixes

* Fixes

* Remove EnsureOneOf

* Fixes

* Fixes

* Fixes

* Formatting

* Fixes

* Update frame/support/src/traits/dispatch.rs

Co-authored-by: Kian Paimani <[email protected]>

* Grumbles

* Formatting

* Fixes

* APIs of VoteTally should include class

* Fixes

* Fix overlay prefix removal result

* Second part of the overlay prefix removal fix.

* Formatting

* Fixes

* Add some tests and make clear rounding algo

* Fixes

* Formatting

* Revert questionable fix

* Introduce test for kill_prefix

* Fixes

* Formatting

* Fixes

* Fix possible overflow

* Docs

* Add benchmark test

* Formatting

* Update frame/referenda/src/types.rs

Co-authored-by: Keith Yeung <[email protected]>

* Docs

* Fixes

* Use latest API in tests

* Formatting

* Whitespace

* Use latest API in tests

Co-authored-by: Kian Paimani <[email protected]>
Co-authored-by: Keith Yeung <[email protected]>