Improve understandability of RAR name mismatch

When ResolveAssemblyReferences rejects a file because the names don't match, it isn't always super clear about why.

```
Primary reference "System.Runtime". (TaskId:24)
...
Considered "d:\CxCache-Scope\DotNetFxRefAssemblies.Corext.4.5.2\Facades\System.Runtime.dll", but its name "System.Runtime, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" didn't match. (TaskId:24)
```

It would be nice to have some sort of clearer error, like "version doesn't match", or even just an aligned set of strings for "expected" and "actual", maybe with markers on another line indicating where the diff begins.

[This is a suggestion from an Microsoft dev on an internal alias.]