Refactor: fixed point arithmetic for SRML. (#3456)

* Macro-ify perthings.

* Refactor fixed64

* Half-workign phragmen refactor.

* Finalize phragmen refactor.

* Fix creation of perquintill

* Fix build errors

* Line-width

* Fix more build errors.

* Line-width

* Fix offence test

* Resolve all TODOs.

* Apply suggestions from code review

Co-Authored-By: Gavin Wood <[email protected]>
Co-Authored-By: thiolliere <[email protected]>

* Fix most of the review comments.

* Updates to multiply by rational

* Fxi build

* Fix abs issue with Fixed64

* Fix tests and improvements.

* Fix build

* Remove more tests from staking.

* Review comments.

* Add fuzzing stuff.

* Better fuzzing

* Better doc.

* Bump.

* Master.into()

* A bit more hardening.

* Final nits.

* Update lock

* Fix indent.

* Revert lock file.

* Bump.