Migrate pallet-grandpa to attribute macros (#8724)

* frame/grandpa: migrate Config

* frame/grandpa: migrate decl_module

* frame/grandpa: migrate decl_event

* frame/grandpa: migrate decl_error

* frame/grandpa: migrate decl_storage

* frame/grandpa: make report_equivocation_unsigned pub(super)

* frame/grandpa: remove unused imports

* frame/grandpa: replace deprecated Module with Pallet

* frame/grandpa: add RawEvent for compatibility

* frame/grandpa: create migration to new storage prefix

* frame/grandpa: bump version to 4.0.0

* frame/grandpa: address review comments

* Try using version 3.1 instead

* frame/grandpa: tweak log text to say cancelled