Implement ConvertSubnetTx

[ruijialin-avalabs]

This PR adds ConvertSubnetTx to pvm etna builder.

• added ConvertSubnetTx to pvm codec at index 35

• added serializable object ConvertSubnetTx and ConvertSubnetValidator

• moved getMemoComplexity to pvm/txs/fee/complexity.ts and renamed it to getBytesComplexity.

• added getSubnetValidatorsComplexity and convertSubnetTx to pvm/txs/fee/complexity.ts

• added INTRINSIC_CONVERT_SUBNET_VALIDATOR_COMPLEXITIES and INTRINSIC_CONVERT_SUBNET_TX_COMPLEXITIES

• added isConvertSubnetTx typeguard

• add NODE_ID, BLS_SIGNATURE, and BLS_PUBLIC_KEY to getEnvVars. which gets the value from info.getNodeId for the network

• added examples to createSubnetTx, createChainTx, convertSubnetTx
  -createSubnetTx and createChainTx have to be issued first before convertSubnetTx can be issued.

• Successful txs in etna explorer for address P-custom1s4k9fch6uyhvv7necq070nzljgrqvazkpgles6:

  1. createSubnetTx
  2. createChainTx
  3. convertSubnetTx

[erictaylor]

Looking good.

Left some initial comments. Let's make sure we are adding test coverage.

[rictorlome]

Thank you! Also, could you please add the new builder function to the etna-examples folder? Feel free to add createSubnet too, so we can verify this. Also, please link to a successful tx in the etna explorer, to confirm the network accepts this tx. Thanks

[erictaylor]

Looks great. Couple small cleanup requests.

[rictorlome]

Thank you. Can this be added to the burn checker as well?