Fix/devnet pox and stacking

[hugocaillard]

Description

Add a few fixes and improvement to be released as 2.2.1

• The publish_stacking_order formula wasn't working on some edge case

  • duration = 1
  • start_at_cycle > duration
    The new formula is slightly simpler (still a bit complicated but well..) and it works in all cases

• Handle the reward_cycle_length property in PoxInfo and revert the regression on reward_phase_block_length

  • This fix requires the update on chainhook

• In the devnet UI, avoid multiple > in case a nakamoto block is mined at the same block height as the beginning of a new pox cycle (eg – [12]> – [11]> – <[10] –)

• use a fixed tag for the hirosystems/stacks-blockchain-api docker image (because :nakamoto is updated frequently)

[MicaiahReid]

LGTM!