Make UseSingularNouns rule work on PowerShell Core

[bergmeister]

PR Summary

Fixes #1626

This uses the open source Pluralize.NET NuGet package, which uses the MIT licence. The added payload is only 20KB once.
Also enhance existing code to not construct Pluralizationservice in foreach loop.

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Change is not breaking
• Make sure all .cs, .ps1 and .psm1 files have the correct copyright header
• Make sure you've added a new test if existing tests do not effectively test the code changed and/or updated documentation
• This PR is ready to merge and is not Work in Progress.
  • If the PR is work in progress, please add the prefix WIP: to the beginning of the title and remove the prefix when the PR is ready.

[SydneyhSmith]

Ah unfortunately, the fact that the package is unlicensed does block us from accepting it

[bergmeister]

Ok, will contact the author if an MIT license or something similar can be added as it was probably not intentional by the author. Would the licence need to be on the NuGet package or just the source repo?
Alternatively, there is a similar NuGet package with MIT license but that is not preferred as the implementation is different to the one that I suggested, which is just a .Net Core port.
https://github.com/sarathkcm/Pluralize.NET

[bergmeister]

@SydneyhSmith I updated it to use the Pluralize.NET library instead, which has an MIT licence.

[SydneyhSmith]

Thanks @bergmeister that package looks good to us