Refactoring request: nullable values to ?? syntax

I would love to have some refactor tool that could suggest non-nullable variables from my parameters or any variable. So when the cursor is on the parameters, it can suggest to insert code:

**Actual Behavior**:
```csharp

MyMethod(int? intOrNull, string? strOrNull)
{
...
}
```

**Expected Behavior**:
```csharp
MyMethod(int? intOrNull, string? strOrNull)
{

// Suggested refactor: Convert null, to 0
Int intOrNullParam = intOrNullParam ?? 0;

// Suggested refactor: Convert null to empty string
string strOrNullParam= strOrNull ?? "";

...
}
```

**What would be the best solution here?**

Should also handle variables:
```csharp
bool? boolOrNull = null

// Suggested refactor: Convert bool to false
bool boolOrNullVar = boolOrNull ?? false
```

What would be the best solution here?

---
Similar issue:
https://github.com/dotnet/roslynator/issues/411

No source file or test is named. Start by reviewing the related Roslynator issue 411 and the existing refactoring approach in this Roslyn-powered project, then define the supported nullable cases and replacement-value rules; done means the scope is agreed and the behavior is covered by tests.

Written by the indexing model from the issue text.