Change how requests are resolved to have strict order

The original implementation tries to satisfy maximum number of requests
in given priority level. This has been seen as ideal solution because
this way most of the user's requests are satisfied.
This changes this behavior to rather be strictly defined. This means
that we do not care about number of requests satisfied. We care only
about priority of request and satisfy them in order.

This also removes error raised when there was Install and Uninstall
request for same package with same priority. Now Install request is
simply preferred.

This was required because of conditions. The demonstration of this issue
can be done on two packages. Let's have package 'a' and 'b'. There are
three requests of same priority:
* To install 'a'
* To unistall 'b'
* To install 'b' with condition 'a'
The intuitive resolution is that user clearly wants to install 'a' and
not to have 'b'. The third request need not apply as there is more
accurate request to not have 'b'.
The original implementation tries to solve this by maximizing number of
satisfied requests. This has three solution, which is on its own pretty
problematic. The first solution is the intuitive one. Second solution is
to install 'a' as well as 'b'. But the third solution is to not install
any package. This is because third request can be satisfied either by
installing 'b' or by not installing 'a'. All of these solutions are
equivalent in solvers conditions as they all result in only one of the
requests to not be satisfied, thus we have no direct way to hint solver
what to do. What is even worst we even don't know what should be the
correct solution without defining additional resolution rules.

Using the new algorithm the solution for problematic request combination
is simply that we order them using our new defined rules, that is also
the order they are ordered in example. Now we take and resolve one
request at the time. We can clearly satisfy installation of 'a' and thus
first request. We can also satisfy not-installation of 'b' and thus
second request. The third request now can't be satisfied and thus
resulting in just 'a' installed.

Full order rules are described in documentation. Reasoning for them is
also hinted but to be complete there are also alternative orders we
could choose. The reasoning is as follows:
* We need to resolve critical packages first to make sure that all of
  them can be satisfied (so we would not close some combination by
  regular requests).
* The user specified priority has to be abided.
* The requests without condition are preferred as they clearly state
  what should happen. Conditions can have side effect such as forcing
  some specific combination to satisfy given request. This is of course
  highly undesirable as condition should control only if request is
  satisfied not to influence packages specified in condition. Given the
  nature of satisfiability solver this backward injection is just going
  to happen so we instead simply prioritize requests that have no such
  effect.
* Another major change buried in these changes is that Install and
  Uninstall requests for same package no longer raise error. We prefer
  Install requests as a choice. The removal of error is because it was
  arbitrary anyway. There are simple ways Install and Unistall requests
  can be in direct collision without specifying same package name, such
  example being if package 'a' depends on 'b' and there is request to
  install 'a' and to unistall 'b'.
* The last resort order is order of definition is scripts. In the effect
  this is not that important. This affects only requests that have same
  priority, same type (install or uninstall) and both have or not have
  condition. Such requests effectively want the same thing so they
  hopefully should not collide that much in their requests.
7 jobs for fix-condition-injection in 4 minutes and 26 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #520421
build-alpine

00:01:38

passed #520419
build-debian-stable

00:01:34

passed #520420
build-debian-unstable

00:01:33

 
  Test
passed #520422
check

00:01:33

passed #520424
lint-c

00:00:38

passed #520425
lint-lua

00:00:38

passed #520423
valgrind-memcheck

00:02:47