Add .NET Framework assemblies to 5.0

[dougbu]

• and let their assembly versions change

[dougbu]

.NET Framework 4.7.2 has broad support across Windows versions and should be supported for w while. I'm basing this on https://docs.microsoft.com/en-us/lifecycle/faq/dotnet-framework.

In any case, let's use the net472 TFM when we fix this issue.

[Pilchie]

Consider using net461 instead of net472, as it means that people on that framework won't fall into the netstandard version and end up with facade issues.

[dougbu]

Sounds good @Pilchie

[dougbu]

This issue is specific to implementation (not tooling) projects containing shipped netstandard2.0 (or lower) assemblies

[wtgodbe]

Following files (and a few others) may need some tweaking of their #if blocks that are TFM-specific:

• src\DataProtection\Cryptography.KeyDerivation\src\PBKDF2\NetCorePbkdf2Provider.cs
• src\Identity\Extensions.Core\src\PasswordHasher.cs
• src\Shared\WebEncoders\WebEncoders.cs
• src\SignalR\common\Shared\MemoryBufferWriter.cs
• src\SignalR\common\Shared\PipeWriterStream.cs

[wtgodbe]

Resolved by #25094