Add ImplementingType to RuleInfo object

[JamesWTruher]

PR Summary

This will enable easier creation of settings file validation and settings file template creation.
Navigating to the actual implementation of the rule is quite difficult, by providing the implementing type of the rule, this becomes much easier. This is similar to how CmdletInfo works in PowerShell where there is an ImplementingType property on the CmdletInfo object.

This will enable a couple of things; first, we'll be able to create validation of settings file without translating the rule name to the type that implements (so you can very easily retrieve the configurable properties). Second, it will also be possible to write tools to create templates for settings.

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
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[bergmeister]

Apart from a small comment about a property, looks good to me, thanks.

[bergmeister]

I think the CA rule is right to call this out. C# has auto-properties now that can simplify this property to public Type { get; } whereby the private setter is included by default.

[JamesWTruher]

yah - I didn't want to change them all, so I just followed the previous example for consistency. I'm certainly happy to change all of them.