SDK Improvement to switch between different already created wallets

[SergiExec]

When we create a new wallet, by default, the SDK uses the last wallet we have created. In order to use a different wallet one time, we must first find the wallet address we want to use, copy it and paste it in the respective command using the label --wallet-address (e.g. iexec app deploy --wallet-address 0xDf16d29E83E227160B23B2203XXXXXXXXX). I propose an improvement in this aspect: to be able to change the wallet we are using with a single command:
(e.g. iexec wallet switch or change 0xDf16d29E83E227160B23B2203XXXXXXXXX) then: iexec app deploy and in this way not have to go looking for the wallet address every time we want to use it if we pretend to do more actions with this wallet, not just once.