(#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.  We also reduce the log level to
'info' for any other parse failures.
(#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.  It also turns down logging on invalid rpm -q
lines from warning to info.
(#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...