The existential deposit. Set to 1/10 of the Connected Relay Chain.
We allow for 0.5 of a second of compute with a 12 second average block time.
NOTE: reduced by half comparing to origin impl as we want to fill block only up to 50%
so there is room for new extrinsics in the next block
This determines the average expected block time that we are targeting.
Blocks will be produced at a minimum duration defined by SLOT_DURATION.
SLOT_DURATION is picked up by pallet_timestamp which is in turn picked
up by pallet_aura to implement fn slot_duration().