Use copy module instead of BaseModel.copy()

[pederhan]

In pydantic V2, the .copy() method will be removed from models and replaced with the ability to use the built-in copy module to copy models.

We use copying to take a copy of the config before it is modified by REPL commands, so that we can restore the overridden values after the command has been executed:

https://github.com/pederhan/harbor-cli/blob/bf929a6229953512eb7a6c9b57ecb52c874854d4/harbor_cli/main.py#L226-L233