Add global upgrade and global upgrade-all command

[trueleo]

Problem description

Description

Pixi currently provides global install to install binary packages globally. However there is no upgrade subcommand to upgrade packages.

There is an existing issue where people have commented about wanting this feature.

Note / Ideas

• pixi global install can be used to upgrade a single package. So maybe upgrade subcommand can just be alias/proxy to install command.

[ruben-arts]

Perhaps we could move even more into an fn globally_install_package or whatever the best name would be and the call that function in both the install and upgrade commands. Then we can keep the info for the user as you have done it now. Including the checking if the package is available (which I would indeed make an error).
Edit: this was meant for the PR #614