Create new flag to non interactively display what's available to upgrade

[rightaway]

Describe the solution you'd like

yay --sync --combinedupgrade --sysupgrade shows the output of available packages to upgrade in a very nice looking and useful way. It shows things in columns categorized by type of repository, and in color, with appropriate highlighting.

There should be a flag we can pass to just show this output which is non interactive, so it doesn't prompt for a Y/N and doesn't require any keyboard input. Just displays and quits, exactly how yay -Qu does.

Then our custom upgrade scripts and reports can get the benefit of having the same excellent formatting of the other command. For example you can do something like whenever you log in to your system the terminal prints this nice output so you can decide if you want to upgrade at a glance.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[rightaway]

?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[rightaway]

@Jguer

[Jguer]

Sorry @rightaway , I've added this as approved for stable bot to keep away from it.

I still have some doubts as I'm not sure under which command we'd put it in