Implementation CodeLens (`ImpLens`)

# The Issue

When implementing an `interface` / `abstract class`, it can be very obscure which members are actually implementing it.

# Describe the solution you would like

Add a CodeLens above the member implementing the `interface`.

Here is an example of a CodeLens (the CodeLens is the small text saying `references`):


The CodeLens ideally should have a special symbol next to it.

---

Example of desired CodeLens:

    Implements IEnumerable<int>
```cs
public bool MoveNext() => position < _people.Length;
```

# Applicable Scenarios

Ideally, there should be a setting for this (disabled by default).

This will apply to any member that is an implementation of an `interface` / `abstract class`.