Investigate Substrate Fast-Sync and Possible Gossamer Implementation

[danforbes]

Issue summary

• Substrate implements a "fast sync" mode, however, it's not clear if this will be superseded by a "warp sync" mode. This Epic is for investigating Substrate fast sync in order to determine how important it is for it to be implemented in Gossamer. If implementing fast sync is deemed a priority, this Epic will track its implementation in Gossamer.

Other information and links

• Substrate fast sync PR

[FlorianFranzen]

https://spec.polkadot.network/#sect-network-sync