Bounties Pallet to FrameV2 (#9566)

* migrate bounties pallet

* events in tests

* test import event

* Update frame/bounties/src/lib.rs

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

* cargo fmt

* line width

* benchmarks compile

* add migrations

* fmt

* comments

* mod migrations

* fix Cargo.toml

* never remember cargo fmt

* fix migration

* migrations and test

* change checks in migration

* remove unused values

* Update frame/bounties/src/migrations/v4.rs

* cargo fmt

* fix benchmarking

* trigger ci

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