Exclude conflicting type names from import completion

[citizenmatt]

Adds Boo.Lang.* and UnityScript.* as namespaces to be excluded from auto-import. Also adds System.Diagnostics.Debug as a method to be ignored. This means that these namespaces and types are not shown in import completion popup lists, the auto-import tooltip popup, and any other quick fix. The only way to use these types is to manually add the using statement.

This addresses the issue that trying to complete List<T> can match Boo.Lang.List<T>.

This PR also adds an internal action to Rider that will dump all duplicate type names in a given project. Useful to show candidates that could use further rules.

Fixes #574

[SugoiDev]

Ignoring System.Diagnostics.Debug will help a lot, since it is often the first choice when you use a Debug.Log* method and is always the wrong one.

I would really like to see this generalized to allow the user to add a new import completion ignore list.
There are quite a few DLLs in third party packages that, despite having public methods, should never be used. In particular obfuscated ones that only add noise.

[citizenmatt]

This is already a generalised mechanism. This PR will add default entries into the Preferences | Editor | General | Auto Import settings page. You're free to add your own.

[citizenmatt]

Other candidates for exclusion:

• System.Numerics.Vector2, Vector3, Vector4, Quaternion and Plane conflict with the same types in UnityEngine. I think this is probably worth adding. In the context of Unity, you'll want to use the Unity types, as that's what the Unity APIs will expect.
• System.Random and UnityEngine.Random. There is an argument for using System.Random - it's an object, so you can create a separate random source for different consumers, you can create an instance with a given feed so you can make it a little more reproducible, etc. But you can also argue those are advanced use cases, so it's ok to make you add the using manually.

Comments?

[citizenmatt]

Merged as-is. We'll review System.Numerics and Random during the EAP.

[citizenmatt]

See also RIDER-33445

[keith-miller]

Thank you so much for this!