feat(node): support BLS staking key + custom network genesis

[Nuttymoon]

Changes

• avalanche.node
  • Support providing a BLS key as staking key (used by AWM)
  • Support providing a custom genesis file to create a custom network (not mainnet, testnet|fuji or local)
• Update license header

Breaking changes

• avalanche.node
  • Variable avalanchego_staking_certs_dir was renamed to avalanchego_staking_dir
  • Rename node.(crt|key) to staker.(crt|key) to match AvalancheGo default

Additional comment

The BLS key file for a node has to be provided as {{ inventory_hostname }}.bls.key in the local staking dir.