Install and download subcommand conclusion needs improving

[McSinyx]

I wonder if this is a good chance to change the output format as well. The current space-delimited format is very difficult to parse, both visually or by a program.

The same actually applies to the “successfully installed” message for pip install as well. Would a PR changing it to, say, one package on a line, be welcomed?

Originally posted by @uranusjr in #8709 (comment)

Currently this is how they look like (I'm using a screenshot to show the hard line breaks):

The following is the output of aptitude, which put all (also space-delimited) packages name to a separate block and soft wrap them:

# aptitude safe-upgrade 
Resolving dependencies...                
The following NEW packages will be installed:
  libdaxctl1{a} libjs-highlight.js{a} libmujs1{a} libndctl6{a} libstd-rust-1.45{a} 
The following packages will be REMOVED:
  ant-contrib{u} libstd-rust-1.43{u} libx264-155{u} 
The following packages will be upgraded:
  bash bash-completion bsdmainutils calendar flatpak gstreamer1.0-plugins-ugly 
  gstreamer1.0-plugins-ugly-dbg gstreamer1.0-plugins-ugly-doc libblas3 libc-bin 
  libc-dev-bin libc-l10n libc6 libc6:i386 libc6-dbg libc6-dev libc6-dev-i386 
  libc6-dev-x32 libc6-i386 libc6-x32 libcap2 libcap2-bin libfreexl1 libglade2-0 
  libguice-java libheif1 libkf5coreaddons-data libkf5coreaddons5 libkf5js5 
  libkf5jsapi5 libkf5kexiv2-15.0.0 liblapack-dev liblapack3 libmatroska7 
  libmodule-scandeps-perl libnode-dev libnode72 libpmem1 libportaudio2 
  libqt5designer5 libqt5help5 libqt5webkit5 libserializer-java 
  libsource-highlight-common libsource-highlight4v5 libspectre1 libstd-rust-dev 
  libstemmer0d libzstd-dev libzstd1 libzstd1:i386 locales mkvtoolnix mupdf-tools 
  ncal:i386 nodejs nodejs-doc ovmf pandoc pandoc-data pci.ids python3-cryptography 
  python3-socks qemu-system-common qemu-system-data qemu-user-static qemu-utils 
  ruby-childprocess rust-gdb rustc texlive-lang-greek texlive-lang-other vokoscreen 
  vokoscreen-ng 
The following packages are RECOMMENDED but will NOT be installed:
  libpam-cap 
74 packages upgraded, 5 newly installed, 3 to remove and 2 not upgraded.
Need to get 296 MB of archives. After unpacking 9,557 kB will be used.
Do you want to continue? [Y/n/?]

One other alternatives I can think of are comma-delimited and newline-delimited lists. I'm also wondering if we want to change the format used to report the version so that uninstallation is copy-pastable, e.g. appdirs==1.4.4 instead of appdirs-1.4.4.

[uranusjr]

Comma-separated is probably worse than space-separated IMO, since the extra comma actually adds visual noise and makes it even harder to parse by a machine.

[pradyunsg]

@nlhkabu @ei8fdb Flagging for your attention, related to #8453.