Refactor ResizeBehavior to use List<T> instead of ArrayList

[elachlan]

• Refactor ResizeBehavior to use List<T> instead of ArrayList
• Refactor ResizeComponent.resizeControl from object to Control to remove casting

Related: #8140

Microsoft Reviewers: Open in CodeFlow

[elachlan]

@lonitra test failure looks unusual and unrelated:

Process terminated. Encountered infinite recursion while looking up resource 'Arg_NullReferenceException' in System.Private.CoreLib. Verify the installation of .NET is complete and does not need repairing, and that the state of the process has not become corrupted.
   at System.Environment.FailFast(System.String)
   at System.SR.InternalGetResourceString(System.String)
   at System.SR.GetResourceString(System.String)
   at System.NullReferenceException..ctor()
   at System.Resources.ResourceManager.GetString(System.String, System.Globalization.CultureInfo)
   at System.SR.InternalGetResourceString(System.String)
   at System.SR.GetResourceString(System.String)
   at System.NullReferenceException..ctor()
   at System.Windows.Forms.Application+ThreadContext.FromCurrent()
   at System.Windows.Forms.Application.FormActivated(Boolean, Boolean)
   at System.Windows.Forms.Form.WmActivate(System.Windows.Forms.Message ByRef)
   at System.Windows.Forms.Form.WndProc(System.Windows.Forms.Message ByRef)
   at System.Windows.Forms.NativeWindow.Callback(Windows.Win32.Foundation.HWND, Windows.Win32.MessageId, Windows.Win32.Foundation.W

[lonitra]

Agree this looks unrelated. Reran the tests. Will take a look at this PR soon

[lonitra]

LGTM