(#22529) Dpkg provider does not warn on package not found

e96ac6 (#19875) extended the dpkg and rpm providers to obtain package
descriptions, and the change in the regex meant that dpkg-query's 'No
packages found matching foo' output for non-existent packages was no
longer being silently swallowed, and instead began triggering the
warning log.

In this commit we explicitly guard against dpkg-query's package not
found message triggering a warning.
(#22529) Rpm provider does not parse 'package foo is not installed' as a package

Rpm provider previously parsed 'package foo is not installed' as if that
was valid package info returned by an rpm -q call.

In line with changes to dpkg provider, this commit also skip rpm's
'package ... is not installed' message without logging or returning an
erroneous package hash.
(#22529) Acceptance test for puppet package resource behavior

Checking expected output for packages that do not exist.
(maint) Convert from should to expect syntax

Since I was touching the dpkg/rpm_spec...