Columnar output for package lists similar to 'ls'

This change makes it a bit easier to quickly grasp the changes
about to be performed by apt.

It displays package lists in a columnar format by default,
similar to what `ls` produces for files.

A new long option `--no-list-columns` and an associated
`APT::Get::List-Columns` config setting control the behavior.

Usage example, with 60 column wide terminal:

```
$ sudo apt upgrade                                          |
Reading package lists... Done                               |
Building dependency tree... Done                            |
Reading state information... Done                           |
Calculating upgrade... Done                                 |
The following packages were automatically installed and are |
no longer required:                                         |
  libappindicator1 libindicator7                            |
  libdbusmenu-gtk4 linux-image-5.14.0-4-amd64               |
Use 'sudo apt autoremove' to remove them.                   |
The following packages have been kept back:                 |
  criu        linux-headers-amd64 nvidia-settings           |
  libxnvctrl0 nvidia-modprobe     xwayland                  |
0 upgraded, 0 newly installed, 0 to remove and 6 not upgrade|
d.                                                          |
```

The effect becomes more pronounced with more packages (e.g. when
doing a dist-upgrade).

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