Fix tool when using under .NET 6 for real this time.

[AraHaan]

After trying the current preview tool as I must use the preview EFCore builds with .NET 6 due to reasons I cannot control. I still had the tool be broken even with the roll forward. As such I have discovered the reason for this is because of the fact that for some reason even roll forward did not properly tell it how to run as if the tool were compiled for .NET 6. As such the tool had to be patched to change .NET Core 2.0 to .NET 6 in order to get it to work.

Fixes #27660 (comment).

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        Summary of the changes
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        Fixes #bugnumber

• Tests for the changes have been added (for bug fixes / features) No need, this just fixes the tool to run with only the .NET 6 SDK and runtime installed. For some reason my previous PR that only changed RollForward was not enough.
• Code follows the same patterns and style as existing code in this repo

[ajcvickers]

@AraHaan Dropping netcoreapp2.0 is not something we can currently do.

[AraHaan]

I guess an option could be to check the .NET SDK's version to see if it's 6.0.xxx and if so, use the .NET 6 target of the tool, else use netcoreapp2.0 (if not .NET Framework). However it would require an additional dependency.

[ajcvickers]

Closing as this isn't something we plan to do at this time.