massa-client should support mainnet (or buildnet) url instead of ip

[sydhds]

Is your feature request related to a problem? Please describe.

Using the massa-client with one of the ip behing mainnet.massa.net is blocked. It could be useful if your node is down (server upgrading, massa node version upgrading) and you still want to transfer some coins.

Describe the solution you'd like

So would be nice to be able to specify directly the url (https://mainnet.massa.net/api/v2). So at the end, we could run the massa-client like:

massa-client -u https://mainnet.massa.net/api/v2 ...

Describe alternatives you've considered

N/A

Additional context

N/A