[dotnet-format] Include the .NET Framework buildhost executable in the SDK.

[JoeRobich]

This is necessary for dotnet-format to load .NET Framework projects.

Backport of #45290 to release/8.0.4xx

Description

Roslyn 4.9+ moved project loading out-of-process to a separate build host. Roslyn ships both .NET and .NET Framework build hosts in order to support framework projects. By not shipping the full framework build host dotnet-format now errors when trying to load full framework projects.

Risk

Low - This same change has shipped in the 9.0 SDKs and is not a change in behavior but a packaging change.

Regression

Yes. Prior to moving to Roslyn 4.9+ full framework projects were not supported by dotnet-format and there would be no error.

Testing

[marcpopMSFT]

@arunchndr @JoeRobich is this needed for July servicing and can you update the tactics template and send mail for approval?