[Proposal] `?=` operator: New If Nothing

I have a param `reqAttrs As List(Of String)` which I need to initialize it if nothing like this:

```VB.NET
reqAttrs = If(reqAttrs, New List(Of String))
```

I hope this can be shorten using null coalesce like this
```VB.NET
reqAttrs? = New List(Of String)
```

And I hope we don't mention the type and generic param since they are well known, I saw this proposal once, here or in C# repo and I hope it is done for all initializations:

```VB.NET
reqAttrs? = New
```

Or format it as:
```VB.NET
reqAttrs ?= New
```

Compare this to:
```VB.NET
reqAttrs = If(reqAttrs, New List(Of String))
```

If someone fears that `?=` is too symbolic and less readable, the alternative verbose VB one can be:

Or format it as:
```VB.NET
reqAttrs = New If Nothing
```