* add ClassAccount to uniques storage

* add tests for Class and ClassAccount storage

* fix format

* fix description

* add migration

* remove extra iteration

* Update frame/uniques/src/migration.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* cargo run --quiet --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_uniques --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/uniques/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* fix format

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: Parity Bot <admin@parity.io>
Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>