Update templates to use ApplicationConfiguration.Initialize()

[RussKie]

Relates to #5035
Relates to #5071

Proposed changes

• Update template for .NET 6.0+ apps replacing Application.* boilerplate with the new ApplicationConfiguration generated method introduced in https://github.com/dotnet/designs/blob/main/accepted/2021/winforms/streamline-application-bootstrap.md

Regression?

• No, new functionality

Risk

• Minimal

Test methodology

Manually create various apps and verify the expected content

dotnet new -i C:\Development\winforms\pkg\Microsoft.Dotnet.WinForms.ProjectTemplates\content\WinFormsApplication-CSharp
cd .. && md template1 && cd template1 && dotnet new winforms  && code . 
cd .. && md template2 && cd template2 && dotnet new winforms -f net6.0 && code . 
cd .. && md template3 && cd template3 && dotnet new winforms -f net5.0 && code . 
cd .. && md template4 && cd template4 && dotnet new winforms -f netcoreapp3.1 && code . 

Microsoft Reviewers: Open in CodeFlow

[RussKie]

Approved over email