For next relaunch mainnet: Make babe epoch = 1 hour

[icodezjb]

• Goals: Expand epoch_duration to 1 hour, leaving enough time for Validator to maintain validator nodes

• Before change: epoch_duration = session_duration = rewards_cycle = 5 minutes in Babe, xstaking_era = 12 * epoch_duration = 1 hour, The validator set rotates every 1 hour, call mint_and_slash in start_session (every 5 minutes)

• After change: epoch_duration = session_duration = 1 hour, rewards_cycle = 5 minutes in Babe, xstaking_era = epoch_duration = 1 hour, The validator set rotates every 1 hour, call mint_and_slash in on_initialize (every rewards_cycle=5 minutes)

[icodezjb]

TODO : mint and slash should be treated equally