Elastic scaling: runtime v2 descriptor support (#5423)

Closes https://github.com/paritytech/polkadot-sdk/issues/5045 and
https://github.com/paritytech/polkadot-sdk/issues/5046

<del>On top of
https://github.com/paritytech/polkadot-sdk/pull/5362</del>

TODO:
- [x] storage migration for allowed relay parents tracker 
- [x] check session index
- [x] PRdoc
- [x] tests
- [x] ensure UMP queue cannot be abused with this change
- [x] Zombienet runtime upgrade test

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Signed-off-by: Andrei Sandu <[email protected]>