Move Razor and Blazor WASM SDK into the dotnet/sdk repo

[mkArtakMSFT]

There are multiple issues associated with the current approach, where we build the Razor SDK on the fly, when we try to test it.
One of the main problems is that this results in some files to be locked and eventually failing any subsequent builds.

Note: this problem happens only during local development.
It doesn't happen on CI builds as we don't do incremental builds. We just run multiple distinct builds with different target architectures.

Thanks for contacting us.
We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. We will evaluate the request when we are planning the work for the next milestone. To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[dougbu]

/fyi @dotnet/aspnet-build

[dougbu]

Sample error in later builds, after changing something that causes a Razor SDK project to rebuild:

...\aspnetcore\src\Razor\Microsoft.NET.Sdk.Razor\src\Microsoft.NET.Sdk.Razor.csproj(97,5): error MSB3026: Could not copy "...\aspnetcore\artifacts\bin\Microsoft.NET.Sdk.Razor\Debug\net46\Microsoft.NET.Sdk.Razor.Tasks.dll" to "...\aspnetcore\artifacts\bin\Microsoft.NET.Sdk.Razor\Debug\sdk-output\tasks\net46\Microsoft.NET.Sdk.Razor.Tasks.dll". Beginning retry 1 in 1000ms. The process cannot access the file '...\aspnetcore\artifacts\bin\Microsoft.NET.Sdk.Razor\Debug\sdk-output\tasks\net46\Microsoft.NET.Sdk.Razor.Tasks.dll' because it is being used by another process.
...
...\aspnetcore\src\Razor\Microsoft.NET.Sdk.Razor\src\Microsoft.NET.Sdk.Razor.csproj(97,5): error MSB3027: Could not copy "...\aspnetcore\artifacts\bin\Microsoft.NET.Sdk.Razor\Debug\net46\Microsoft.NET.Sdk.Razor.Tasks.dll" to "...\aspnetcore\artifacts\bin\Microsoft.NET.Sdk.Razor\Debug\sdk-output\tasks\net46\Microsoft.NET.Sdk.Razor.Tasks.dll". Exceeded retry count of 1. Failed.
...
...\aspnetcore\src\Razor\Microsoft.NET.Sdk.Razor\src\Microsoft.NET.Sdk.Razor.csproj(97,5): error MSB3021: Unable to copy file "...\aspnetcore\artifacts\bin\Microsoft.NET.Sdk.Razor\Debug\net46\Microsoft.NET.Sdk.Razor.Tasks.dll" to "...\aspnetcore\artifacts\bin\Microsoft.NET.Sdk.Razor\Debug\sdk-output\tasks\net46\Microsoft.NET.Sdk.Razor.Tasks.dll". The process cannot access the file '...\aspnetcore\artifacts\bin\Microsoft.NET.Sdk.Razor\Debug\sdk-output\tasks\net46\Microsoft.NET.Sdk.Razor.Tasks.dll' because it is being used by another process.
...
...\aspnetcore\src\Razor\Microsoft.NET.Sdk.Razor\src\Microsoft.NET.Sdk.Razor.csproj(97,5): error MSB4181: The "Copy" task returned false but did not log an error.

Each error repeats twice, meaning incremental builds frequently fail with 8 errors. Note this is not a fail-fast scenario unfortunately.