Lib.rs

Implementation of the Prospective Parachains subsystem - this tracks and handles prospective parachain fragments and informs other backing-stage subsystems of work to be done.

This is the main coordinator of work within the node for the collation and backing phases of parachain consensus.

This is primarily an implementation of "Fragment Trees", as described in polkadot_node_subsystem_util::inclusion_emulator.

This subsystem also handles concerns such as the relay-chain being forkful and session changes.