pacman: implement universal transactions

This allows using -S, -U and -R in one command:

    pacman -S foo -R bar

To make this work some breaking changes have made.

Targets have to come after the operation:

    pacman -S foo  //works
    pacman -Syu    //works
    pacman -yuS    //works
    pacman foo -S  //doesn't work

This could be supported with some code to copy all targets before the
first operation into the first operation's target list.

And -u as a short for --unneeded has been removed as it conflicts with
--sysupgrade. However has -u/--sysupgrade is bound to -S, accidently
doing `pacman -Ru` will not accidently cause a system upgrade.

Another quirk with the ui is that -S has many non transaction related
flags, -Sc -Sg -Sl -Si. These have been split off as "sync only" flags.
Meaning they show up with `pacman -Si foo` but will be invalid on
`pacman -R bar -Si foo`.

Also when -R'ing and -S'ing the same package in come command it's
treated as a full uninstall then reinstall. The backup files are
.pacsave'd and the install reason is set to explicit. I feel like this
behavious is good. This also allows you to wipe config files which what
--nokeep was intending to solve.

Other flags just have to have the op they belong to to be used for them
to be valid.

For example:

    pacman -Rn foo //works
    pacman -S -Rn //works
    pacman -Sn    //doesn't work
    pacman -Sn -R //works

We could posibly drop these flags belonging to each operation and just
make them generic transaction flags.

Implements FS#9694
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