add genesis presets for coretime parachains (#7476)

Extracted from #7473.

Part of: https://github.com/paritytech/polkadot-sdk/issues/5704.

---------

Co-authored-by: Guillaume Thiolliere <guillaume.thiolliere@parity.io>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>