"apt" command line tool does not correctly check for terminal capabilities

[Clément]

The new-ish "apt" command draws its progress bar and produces escape codes regardless of advertised terminal capabilities; in particular, with TERM=dumb, "apt" still produces save_cursor and restore_cursor escape codes ("\0337" and "\0338"), in addition to colors and other ANSI escapes.

An example of a commonly used shell with TERM=dump is Emacs' shell buffers. In these, running "apt" produces the following:

```
(Reading database ... 363533 files and directories currently installed.)
Removing wireshark (2.0.2+ga16e22e-1) ...
7Progress: [ 0%] [...............................................................................................] 87Progress: [ 25%] [########################.......................................................................] 87Progress: [ 50%] [################################################...............................................] 87Progress: [ 75%] [########################################################################.......................] 8
78
```

This is due in part to the PackageManagerFancy::DrawStatusLine() function in apt-pkg/install-progress.cc.

Note that Emacs can process and display typical SGR ANSI escapes (in the form [<number>m; but not the more complex cursor manipulation commands.

```
$ apt policy apt
apt:
  Installed: 1.2.12~ubuntu16.04.1
  Candidate: 1.2.12~ubuntu16.04.1
  Version table:
 *** 1.2.12~ubuntu16.04.1 500
        500 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     1.2.10ubuntu1 500
        500 http://archive.ubuntu.com/ubuntu xenial/main amd64 Packages
```

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.