Refactor PluginRunner to OpenUtau.Core and testable

[arkfinn]

• Plugin logic move from ViewModel to OpenUtau.Core.
• Create interface IPlugin.( for unit test)
• Create unit test.

This fix might makes easier for plugins test in future.
But I know we have various concept on coding.
If more good thoughts, would you give me.

[stakira]

DocManager is a Core class. Maybe you don't need OnReplaceNote and OnError events? This will avoid GC complexity around event handlers.

[arkfinn]

Thanks.
I try to more simple method.

This was for the following reasons

1. it is the responsibility of the ViewModel to add undo/redo to plugin process.
2. DocManager has state(undoGroup), there might be a problem with parallel test.
3. To easily mocking at test.

[arkfinn]

@stakira
Sorry, I understand the risks of using EventHandler in WPF.
But using DocManager from PluginRunner makes it difficult to test.
I want to remove the use of EventHandler and keep DocManager replaceable.

How about a fix like this:

• Change OnReplaceNote from event to member variable (delete event += from ViewModel)
• Initialize methods use DocManager
• Test methods that use TestMethod

example:

// for ViewModel
public PluginRunner(PathManager path, DocManager doc) {
  this.replaceMethod = (path, toAdd, toRemove) => {
    doc.doSomething()
  }
  ....
}
// for Test
public PluginRunner(PathManager path, Action replaceMethod) {
  this.replaceMethod = replaceMethod
  ....
}

[arkfinn]

I tried to fix it like this