`MembersFunctionsAndValues` returns no auto property symbol in interface implementation

```fsharp
module Module

type I =
  abstract P1: int with get, set
  abstract P2: int

type T() =
  interface I with
    member val P1 = 1 with get, set
```

Repro:
* Get `T` symbol via `checkResults.GetAllUsesOfAllSymbolsInFile`
* Call `MembersFunctionsAndValues`

Expected: auto property is available in the results
Actual: only separate accessors are returned instead