GrainDirectoryOptions are ignored when using IGrainDirectory

[Mostafa-Goher]

Hello
For certain grain types, we use Redis as a GrainDirectory which forces GrainLocatorResolver to use CachedGrainLocator in which there is a hardcoded LRUBasedGrainDirectoryCache with a hardcoded GrainDirectoryOptions
and that is problematic as the current LRU implementation has an issue, see #8736.

We would like to add a custom implementation of IGrainDirectoryCache to work around the current issue with LRU. However, as far as I can see, that is not possible with a non-default grain directory.

Proposed solution:
Use GrainDirectoryCacheFactory.CreateGrainDirectoryCache to construct the IGrainDirectoryCache in CachedGrainLocator similar to LocalGrainDirectory

Thanks in advance

[Mostafa-Goher]

I also noticed the metric orleans-directory-cache-size.Current only works with the default grain directory, my guess by design? then maybe the name can be more explicit?