Wrong namespace is generated when project name contains invalid namespace chars

[filzrev]

Describe the bug

When project name contains invalid namespace chars.
Microsoft.Testing.Platform.MSBuild package generating TestingPlatformEntryPoint.cs with invalid namespace.

Steps To Reproduce

1. Create New Folder (1) directory.
2. Install TUnit project template with following command

   dotnet new install TUnit.Templates

3. Create test project with following command

   dotnet new TUnit
   dotnet add package TUnit
   dotnet add package Microsoft.Testing.Platform.MSBuild
   

4. Run dotnet build and confirm errors

Expected behavior

Escaped namespace (New_Folder__1_) is generated.

Actual behavior

( char is not escaped.

Additional context

This problems happens when using MTP v1.6.0 or later.

I also confirmed same behavior when using xUnit.v3.

[Youssef1313]

Some code we can reuse to fix this:

https://github.com/dotnet/templating/blob/b0b1283f8c96be35f1b65d4b0c1ec0534d86fc2f/src/Microsoft.TemplateEngine.Orchestrator.RunnableProjects/ValueForms/DefaultSafeNamespaceValueFormFactory.cs#L17-L59