Add prompt for deleting already existing wallet in a directory while using forc-new

raised by @ra0x3 over slack:
if `forc wallet new` is run with a path that contains a wallet, it errors out stating that it should be removed. We wanted to make it like this so that forc-wallet does not remove users' wallet without users' explicit intention.

> forc wallet new
Please enter a password to encrypt this private key:
Please confirm your password:
Error: File or directory already exists at "/Users/rashad/.fuel/wallets/.wallet". Remove the existing file, or provide a different path.

@ra0x3 mentioned maybe we could have a prompt like : `This directory already exists, would you like to delete/ovverride it? Y/n` and ease the process while still getting an explicit intention from the users.