(MODULES-6860) Add dsc_lite feature for confines

[Iristyle]

Similar to puppetlabs-toy-chest/puppetlabs-dsc#350 this is a quick fix that might require some further thought given there are currently two version checks against PowerShell performed in two different ways at different points in the lifecycle.

This builds on #40, but if this is merged first, #40 can be closed.

• Previously when a version of PowerShell older than 5.0.10586.117
  was installed, Puppet would return an error message like:

  Error: Could not find a suitable provider for dsc

  Unfortunately this message did not yield any useful information,
  even with --debug and --verbose turned on, because of the way the
  existing confine check was performed with a confine :true

  To produce a more useful message that is meaningful to users,
  introduce a new feature that performs the same check as the
  confine, but that also will issue an error message (only once)
  that indicates the installed version / required version constraints
  for the module, changing the output to:.

  Error: The dsc_lite module requires PowerShell version 5.0.10586.117 - current version 5.0.10514.6

  The cmdlet Invoke-DscResource was introduced in v5.0, and is necessary for the
  dsc_lite module to function. Further bug fixes, first made available in version
  5.0.10586.117 are also necessary for this module to function.

  To enable this module, please install the latest version of WMF 5+ from Microsoft.\n (file & line not available)

• Note that DSC_LITE_MODULE_POWERSHELL_UPGRADE_MSG is never actually
  shown when the PowerShell version is < 5.0.10586.117 because the
  check occurs too late in the lifecycle of loading providers. The
  confine code has already evaluated, preventing the other messsages
  from being shown. This will be removed in subsequent commit.

• The new feature can be used in place of the previous
  CompatiblePowerShellVersion.compatible_version? check

• The message for DSC_LITE_MODULE_POWERSHELL_UPGRADE_MSG that was
  intended to be shown inside the provider wasn't, since the
  checks made in the type for PowerShell compatibility occurred
  earlier in the Puppet run lifecycle.

• This prevents duplication of version checks in multiple locations

• Remove compatible_powershell_version_spec.rb given the code
  has been removed.

[RandomNoun7]

Change manually verified. Running through adhoc.

[RandomNoun7]

Previous error messge

Error: Could not find a suitable provider for dsc

New error message

Error: The dsc_lite module requires PowerShell version 5.0.10586.117 - current version 2.0\n   (file & line not available)
Error: Could not find a suitable provider for dsc

[Iristyle]

The definition of warn_once is at https://github.com/puppetlabs/puppet/blob/80e7948c69b6c2145a709c6e7fc95bd7bb772f26/lib/puppet/util/logging.rb#L167