Prevent blockchain create from failing after previous failed attempts

[meaghanfitzgerald]

Goal

Enable users to call avalanche blockchain create without fail.

Details

Like documented in #2334, users are unable to successfully call avalanche blockchain create <name> if the call has failed during previous attempts to create a blockchain with the same <name>. In other instances, a user may want to overwrite a blockchain config previously created.

avalanche blockchain create should:

• check if blockchain has already been created
• if yes, ask user "Would you like to overwrite the existing blockchain configuration for ?"
  • if user selects yes, create runs successfully, overwritting the existing configuration
  • if no, prompt user for a new blockchain name

if avalanche blockchain create fails:

• check if a subnet directory has been created, a genesis file and a sidecar was also included in creation
  • if not, clean up .avalanche-cli/subnets/<name>