Improve admin benchmarks (#812)

* Remove destroying outcome assets when market is destroyed or resolved

* Fix tests

* Fix format issue

* Add TODO comment

* Remove asset clean up from swaps::destroy_pool

* admin benchmark update

* Fix tests

* fix admin benchmarks

* remove trailing comma

* add asset categories bench comp

* fix after merge

* apply review suggestion

* use let question mark instead of unwrap

* document benchmark components

* use default_dispute_bond

* Update zrml/prediction-markets/src/benchmarks.rs

Co-authored-by: Malte Kliemann <mail@maltekliemann.com>

* Update zrml/prediction-markets/src/lib.rs

Co-authored-by: Malte Kliemann <mail@maltekliemann.com>

* Update zrml/prediction-markets/src/lib.rs

Co-authored-by: Malte Kliemann <mail@maltekliemann.com>

* apply review suggestion

* Update zrml/prediction-markets/src/lib.rs

Co-authored-by: Malte Kliemann <mail@maltekliemann.com>

* fix disputes_len

* fix clippy

* benchmark admin_move_market_to_resolved

* remove todos

* Update zrml/prediction-markets/src/benchmarks.rs

* Update zrml/prediction-markets/src/benchmarks.rs

Co-authored-by: Vivek Pandya <vivekvpandya@gmail.com>

* Update zrml/prediction-markets/src/benchmarks.rs

Co-authored-by: Vivek Pandya <vivekvpandya@gmail.com>

* Update zrml/prediction-markets/src/benchmarks.rs

Co-authored-by: Vivek Pandya <vivekvpandya@gmail.com>

* Update zrml/prediction-markets/src/benchmarks.rs

Co-authored-by: Vivek Pandya <vivekvpandya@gmail.com>

* Update zrml/prediction-markets/src/benchmarks.rs

Co-authored-by: Malte Kliemann <mail@maltekliemann.com>

* Update zrml/prediction-markets/src/benchmarks.rs

Co-authored-by: Malte Kliemann <mail@maltekliemann.com>

* apply review suggestion

* apply review suggestion

* apply review suggestion

Co-authored-by: Vivek Pandya <vivekvpandya@gmail.com>
Co-authored-by: Malte Kliemann <mail@maltekliemann.com>