Moved presets to the testnet runtimes (#5327)

It is a first step for switching to the `frame-omni-bencher` for CI.

This PR includes several changes related to generating chain specs plus:

- [x] pallet `assigned_slots` fix missing `#[serde(skip)]` for phantom
- [x] pallet `paras_inherent` benchmark fix - cherry-picked from
https://github.com/paritytech/polkadot-sdk/pull/5688
- [x] migrates `get_preset` to the relevant runtimes
- [x] fixes Rococo genesis presets - does not work
https://gitlab.parity.io/parity/mirrors/polkadot-sdk/-/jobs/7317249
- [x] fixes Rococo benchmarks for CI 
- [x] migrate westend genesis
- [x] remove wococo stuff

Closes: https://github.com/paritytech/polkadot-sdk/issues/5680

## Follow-ups
- Fix for frame-omni-bencher
https://github.com/paritytech/polkadot-sdk/pull/5655
- Enable new short-benchmarking CI -
https://github.com/paritytech/polkadot-sdk/pull/5706
- Remove gitlab pipelines for short benchmarking
- refactor all Cumulus runtimes to use `get_preset` -
https://github.com/paritytech/polkadot-sdk/issues/5704
- https://github.com/paritytech/polkadot-sdk/issues/5705
- https://github.com/paritytech/polkadot-sdk/issues/5700
- [ ] Backport to the stable

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Co-authored-by: command-bot <>
Co-authored-by: ordian <[email protected]>