[EVM] Subnet precompile - create subnet

[gztensor]

We need to provide the subnet functionality via precompiles. As a first step, we need to create a new precompile that will allow creating subnets and collecting subnet owner cut.

• Precompile name: subnets
• Methods:
  • register_network: Creates a subnet (calls register_network internally). Makes the ss58 mirror of the caller of this method a subnet owner so that the caller's H160 address will effectively receive owners cut and will be able to set hyperparameters (when this is implemented)
• E2E Tests:
  • Subnet is created
  • ss58 mirror is the subnet owner
  • Subnet owner cut is paid to the H160 address (check the amount, which should be 18% of subnet emission)

[keithtensor]

Done in #1110.