Fix source generated formatters for records with string keys

[dmitry-bym]

Just added fix, all previous tests succesfull but for now im trying to make new ones work, so it's draft for now. Just to be clear I assume that the name of the parameter and the property are the same but in different case.

I didn't want to change logic with stringKey collection logic so i just changed key in ctor lookup, the simpliest fix i see

Fixes #1797

[AArnott]

Thanks! The fix and the tests look spot on!

[dmitry-bym]

@AArnott No problem! could you tell me when there will be packages with these changes i just realy need that in my project?

[AArnott]

You can get the packages from our CI feed: https://dev.azure.com/ils0086/MessagePack-CSharp/_artifacts/feed/MessagePack-CI/NuGet/MessagePack/overview/3.0.46-alpha

Note though that as a CI feed, packages may not be retained forever, so ideally you'd consume them through your own feed that would retain it there.
I'm afraid it's still too early to issue a prerelease to nuget.org as things are really in flux in the develop branch.

I suppose if you want, given a good look at your fix, if you want to cherrypick it to our master branch I can merge it there and we can issue another release from there to nuget.org. If the test doesn't port over well, you can drop it since we have it in develop.

[dmitry-bym]

Thanks! will use pack from ur ci feed