More testing and fuzzing and docs for pools (#12624)

* move pools fuzzing to hongfuzz

* merge more small fixes

* fix all tests

* Update frame/nomination-pools/fuzzer/src/call.rs

Co-authored-by: Gonçalo Pestana <[email protected]>

* remove transactional

* fmt

* fix CI

* fmt

* fix build again

* fix CI

Co-authored-by: Gonçalo Pestana <[email protected]>