Add PSObject boxing support in PesterConfiguration

[indented-automation]

PR Summary

Fixes #1977

• Adds PSObject unboxing support to the GetIDictionaryOrNull extension method.
• Adds custom deserializer for the PesterConfiguration object (requires PowerShell 5 or greater).

PR Checklist

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• Tests are added/update (if required)
• Documentation is updated/added (if required)

[indented-automation]

Bear with me a bit, fixing.

[nohwnd]

Made it a Draft PR, mark it as ready for review when done.

[indented-automation]

I was going to pull out the deserializer code I've written, but instead I've changed it so it's only available to PS 5 and higher. It can, of course, be culled if it's not appropriate.

I wanted to rewrite it into C#, but it was giving me such a hard time, death by reflection.

I'll add some tests in the morning. It'll be interesting to see how the large scale test run works out. A lot of the failures I saw locally are speculatively nothing to do with me :)

[nohwnd]

I've changed it so it's only available to PS 5 and higher. It can, of course, be culled if it's not appropriate.

Yeah, we need to solve this for PS3 and up. I think the same thing happens when you pass the values via -ArgumentList, so it can happen on PS3 as well.

[indented-automation]

Yeah, we need to solve this for PS3 and up. I think the same thing happens when you pass the values via -ArgumentList, so it can happen on PS3 as well.

I'll have another crack at the C# version. It's going to be horrible ;)

[indented-automation]

Just a brief note on this version.

I still use the Update-TypeData commands rather than a Types file.

I found when I used the Types file that the assembly implementing the deserializer had to be loaded before the root module (for psm1) which may have worked if it were possible to require the assembly in the manifest, but not otherwise.

Anyway, it's all compatible with PS 3 now, or at least it is if the test results are accurate :)