CP-9378: add RegisterSubnetValidatorTx to etna-builder

[ruijialin-avalabs]

Description:

• added RegisterSubnetValidatorTx to etna-builder
• created RegisterSubnetValidatorTx class and RegisterSubnetValidator class
• updated typeguards
• added example to issue RegisterSubnetValidatorTx

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Issues:

• RegisterSubnetValidatorTx serialization and deserialization needs to be updated with proper message format
• currently RegisterSubnetValidatorTx.fromBytes is paring the message incorrectly, when running the complexity test, it throw not enough bytes error
• RegisterSubnetValidatorMessage should probably be removed.

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Notes:
Based on what I see in avalanchego e2e flow, to issue RegisterSubnetValidatorTx, we have to go through the following flow

• warpmessage.NewRegisterSubnetValidator: creating the RegisterSubnetValidatorMessage
• registering the validator
  • warp.NewUnsignedMessage: creating the unsigned warp message
  • wrapWarpSignatureRequest(unsignedRegisterSubnetValidator): sending the request to sign the warp message
  • findMessage(genesisPeerMessages, unwrapWarpSignature): getting the signature response
  • warp.NewMessage(unsignedRegisterSubnetValidator): creating the signed warp message to register the validator
  • IssueRegisterSubnetValidatorTx: issuing a RegisterSubnetValidatorTx

[erictaylor]

Closing in favor #391