list os packages and register notification

[foxriver76]

This PR implements:

• Whenever we update the repo, we also check for OS packages
• New category for os pacakge updates
• If OS package updates are available, we will register a notification with all the packages listed
• closes Execute "apt list --upgradable" on Linux systems and inform on updates #2488

[foxriver76]

We have to find the correct command for apt-get list is only available for apt

[Apollon77]

But why we need apt-get?

only I found is "apt-get --simulate upgrade"

[foxriver76]

I am not an expert, maybe all systems which have apt-get also have the apt cli? Not sure about this, then it would be save to remove apt-get entirely. As @AlCalzone had some experience with the package manager, maybe he knows.

[Apollon77]

I also "Think" that both should be there ...

[AlCalzone]

Does this help?
https://askubuntu.com/questions/445384/what-is-the-difference-between-apt-and-apt-get/446484#446484

apt-get may be considered as lower-level and "back-end", and support other APT-based tools. apt is designed for end-users (human) and its output may be changed between versions.

Note from apt(8):

The apt command is meant to be pleasant for end users and does not need
to be backward compatible like apt-get(8).

[AlCalzone]

https://itsfoss.com/apt-vs-apt-get-difference/

the first stable version of apt was released in the year 2014, but people started noticing it in 2016 with the release of Ubuntu 16.04

So unless we want to support some really old systems, only using apt should be okay I think.