Call Application.Run passing ApplicationContext, not MainForm

[PreferLinux]

Passing MainForm prevents WindowsFormsApplicationBase.ShutdownStyle from having any effect. It will always shut down when MainForm closes. This fixes that by passing the WindowsFormsApplicationContext, which handles OnMainFormClosed in a way that considers ShutdownStyle.

[PreferLinux]

Imports System.Windows.Forms
Imports Microsoft.VisualBasic.ApplicationServices

Namespace ShutdownStyleTest
	Public Class ShutdownStyleTest
		Inherits Form
		
		Public Class winformsapp
			inherits WindowsFormsApplicationBase
			Public Sub New()
				MainForm = New ShutdownStyleTest()
				ShutdownStyle = ShutdownMode.AfterAllFormsClose
			End Sub
		End Class
		
		Public Shared Sub Main(args() as String)
			Dim appBase As New winformsapp()
			appBase.Run(args)
		End Sub
		
		Public Sub New()
			Text = "Form 1"
		End Sub
		
		Protected Overrides Sub OnClick(e As EventArgs)
			MyBase.OnClick(e)
			Dim frm as New Form()
			frm.Text = "Form 2"
			frm.Show()
		End Sub
	End Class
End Namespace

Here's a quick example test for the problem. Run the above, click on the form to get a second form, and then close the first form. The correct behaviour is that, due to ShutdownStyle = ShutdownMode.AfterAllFormsClose, only the first form closes while all others remain open. Without the fix in this pull request, all forms close.