Allow `PostDispatchInfo` to disable fees (#6749)

* initial mock

* add test

* remove unneeded clone

* Update frame/support/src/weights.rs

Co-authored-by: Alexander Theißen <alex.theissen@me.com>

* fix compile

* Update frame/support/src/weights.rs

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

* Update frame/sudo/src/lib.rs

Co-authored-by: André Silva <123550+andresilva@users.noreply.github.com>

* Apply suggestions from code review

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

Co-authored-by: Alexander Theißen <alex.theissen@me.com>
Co-authored-by: Alexander Popiak <alexander.popiak@parity.io>
Co-authored-by: André Silva <123550+andresilva@users.noreply.github.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>